Search

Many glial cells provide support for an essential nervous system function. In addition to providing support for neurons, glial cells aid in the maintenance of homeostasis, and form myelin. As a whole, glial cells are the most abundant cells in the central nervous system. The most notable glial cells include oligodendrocytes, Schwann cells, astrocytes, microglia, and ependymal cells. Most glial cells are capable of mitotic division., (Copyright © 2022, StatPearls Publishing LLC.)

Wernicke area was first discovered in 1874 by a German neurologist, Carl Wernicke. It has been identified as 1 of 2 areas found in the cerebral cortex that manages speech. Wernicke area is located in Brodmann area 22, the posterior segment of the superior temporal gyrus in the dominant hemisphere. Since 95% of people have a left dominant hemisphere, the Wernicke area is usually found on the left side. This area encompasses the auditory cortex on the lateral sulcus. Contrast this with Broca's area which is found in the inferior frontal gyrus right above the Sylvian fissure. Because the Wernicke area is responsible for the comprehension of written and spoken language, damage to this area results in a fluent but receptive aphasia. Receptive aphasia may be best described as one who is unable to comprehend/express written or spoken language. The patient will most commonly have fluent speech, but their words will lack meaning. The other aspect of Wernicke aphasia is that the patient has auditory incomprehension. This means an individual is unable to understand what is being spoken to them. Lastly, patients with Wernicke aphasia are unaware of their lack of comprehension. Due to the prominent involvement of the Wernicke area in basal life, various disease etiologies may result in damage to this area. , (Copyright © 2022, StatPearls Publishing LLC.)

Tumors in the spine comprise about 15% of all tumors in the central nervous system. They usually are benign and cause symptoms primarily through compression of the spinal cord and nerves. Spinal tumors can be classified into three groups, based on their locations: extradural, intradural-extramedullary, and intramedullary. Extradural tumors are most common, as they occupy the vertebrae body or structures outside the dura. They are most commonly metastatic. Intradural extramedullary tumors are the second most common and come from the leptomeninges or nerve roots. These tumors are located inside the dura but external from the spinal cord, exemplified by meningiomas or neurofibromas. The least common (2 to 5%) are intramedullary spinal cord tumors (IMSCT); these arise from the spinal cord proper, leading to invasion and destruction of the gray and white matter. Ependymomas and astrocytomas are the most commonly encountered intramedullary spinal cord tumors, followed by hemangioblastomas. Other entities include lipomas, germ cell tumors, gangliogliomas, germinomas, lymphomas, and metastases., (Copyright © 2022, StatPearls Publishing LLC.)

Pfeiffer syndrome (PS, OMIM #101600) is an inherited craniofacial disorder that is associated with primary craniosynostosis, midface hypoplasia, broad thumbs and great toes, and soft tissue syndactyly of hands (usually second and third digits) and feet of varying severity. Most of the affected patients have associated conductive hearing loss. Rudolf Pfeiffer first described a syndrome of acrocephalosyndactyly associated with hypertelorism, antimongoloid slant, broad thumbs, great toes, and normal intelligence in 1964. He reported 8 cases through 3 generations of a family, with two instances of male-to-male transmission, suggesting an autosomal dominant mode of inheritance. It is also known as type V acrocephalosyndactyly, craniofacial-skeletal-dermatologic dysplasia, or Noack syndrome. Acrocephalosyndactyly syndromes involving premature closing of the cranial sutures are: Type I: Apert syndrome. Type II: Vogt/Crouzon syndrome. Type III: Saethre–Chotzen syndrome. Type IV: Waardenburg syndrome. Type V: Pfeiffer syndrome., (Copyright © 2022, StatPearls Publishing LLC.)

Cranial nerve (CN) testing is the physical assessment of the nerves innervating structures within the head and neck. It is widely applicable to emergency and clinic situations and can be performed relatively quickly with equipment that is readily available in the hospital or ambulatory environment.  Abnormalities discovered during the examination can be valuable harbingers of neurologic pathologies, such as mass lesions and early warnings of disease progression that will require urgent intervention (i.e., enlarging intracranial aneurysm).  Cranial nerve testing is a particularly useful part of the continued evaluation of unconscious patients and patients with sequela from neurotrauma, strokes, or intracranial pathology, which require frequent monitoring for worsened function or condition. Higher-level tests such as brainstem auditory evoked potentials (BAEP) typically require a referral and can be performed if abnormalities are revealed on initial cranial nerve testing., (Copyright © 2022, StatPearls Publishing LLC.)

Hyperbaric oxygen therapy of intracranial abscesses refers to the following disorders: cerebral abscess, subdural empyema, and epidural empyema. It is defined as a focal, encapsulated infection of cerebral parenchyma and is caused by a wide array of microorganisms such as bacteria, mycobacteria, protozoa, fungi, or helminths. It is a relatively rare condition, with the incidence estimated at 0.3 to 1.3 per 100,000.  However, this number is believed to be elevated in particular high-risk groups; for example, patients with human immunodeficiency virus (HIV) infection or acquired immune deficiency syndrome (AIDS). There are multiple mechanisms responsible for the development of intracranial abscesses. The infectious organism can invade the brain by either direct spread, which accounts for 20% to 60% of the cases. This is typically caused by a contiguous infection such as sinusitis, otitis, mastoiditis, or dental infection. Brain abscesses can also arise from hematogenous seeding or cranial trauma, which typically manifests as multiple abscesses. Streptococcus and Staphylococcus are the most frequent causes of brain abscesses, with Viridans streptococci  and Staphylococcus aureus being the most common. Anaerobes are also a common constituent of brain abscesses, which originate from the normal oral flora.  A patient’s immune status is also important when considering the cause of the infection. Bacterial abscesses are typically seen in immunocompetent individuals, while immunocompromised patients can be infected with a wide array of organisms, including fungi. Although it is a rare condition, mortality remains at a high rate for patients with brain abscesses. However, one systematic review and meta-analysis demonstrated that the prognosis of patients with brain abscesses has significantly improved. This study showed that over the past 6 decades, the case fatality rate decreased from 40% to 10%, and the rate of patients with full recovery increased from 33% to 70%. Another study, a report in 289 patients with pyogenic brain abscess treated between 1999 and 2006, showed a mortality rate as low as 2.7%. Several factors have been credited towards these improved outcomes. The introduction of computed tomogram (CT) imaging has been critical in improving treatment results for brain abscesses. One retrospective study demonstrated that intracranial abscess mortality rate dropped from 40% to 20% within the first decade after the invention of CT imaging. This invention has allowed clinicians to make a faster diagnosis and facilitated less invasive, more precise neurosurgical procedures such as stereotactic aspiration of abscesses. Improvements in neurologic surgical techniques and antimicrobial therapy, which are the mainstay of therapy, have also been instrumental in these improved outcomes., (Copyright © 2022, StatPearls Publishing LLC.)

Nimodipine is a second-generation 1,4-dihydropyridine calcium channel blocker. It was initially invented for the management of systemic hypertension. FDA approved the use of nimodipine for the first time in 1988. However, its use is restricted mainly in the management of vasospasm following subarachnoid hemorrhage. It also has numerous off-label uses. This activity outlines the indications, mechanism of action, methods of administration, significant adverse effects, contraindications, monitoring, and toxicity of nimodipine, so providers can direct patient therapy successfully in instances where nimodipine provides a benefit to patient care., (Copyright © 2022, StatPearls Publishing LLC.)

First described by Hart in 1830, in the present era an intramedullary spinal cord abscess (ISCA) is a very rare form of spinal cord abscess. Their rarity may be accountable to the following factors: 1. A relatively smaller volume and total surface area of the cord.    . 2. An acute angle of origin of the corresponding spinal arteries.       . 3. The protection is provided by the osseous vertebral canal and the meningeal layers, notably the pia mater. Though rare, prompt diagnosis and treatment of this condition are of paramount importance to preventing damage to the spinal cord that can lead to disabling neurological deficits and possibly death. , (Copyright © 2022, StatPearls Publishing LLC.)

Despite the advances in pharmacotherapy for treating some psychiatric disorders like anxiety disorders, obsessive-compulsive disorder, depression, and schizophrenia, many patients become refractory and will not respond to pharmacologic treatments. Clinicians are beginning to reconsider neuromodulation surgery as a last resort for the treatment of these patients. Neurosurgical interventions aimed at treating psychiatric disorders are grouped into destructive (ablative psychosurgery) or selective stimulation (neuromodulation psychosurgery). Neuromodulation surgery involves implanting a device in the brain that modulates the neural networks within the brain. The use of surgery for the treatment of psychiatric diseases is not a new concept. Historically, the concept of psychosurgery always raised general skepticism and stigma because of the way that it was used in the past with a high rate of complications and mortalities, but usually with little improvement in patients’ functionality. In 1881, Gottlieb Burckhardt, a Swiss psychiatrist, reported on six patients that he performed surgery to treat aggressive behavior and hallucinations with partial results. Three decades later, Puusepp operated in 1910 on three manic-depressive patients by interrupting the frontal fibers to the parietal cortex. Fulton and Jacobsen's classical experiments on two chimpanzees that received frontal lobe surgical ablation to improve neurotic behaviors were an inspiration for subsequent human ablative procedures. In 1935, a Portuguese neurologist named Egas Moniz first introduced a surgical procedure called prefrontal leucotomy. Moniz believed that abnormal connections to the frontal lobe caused some psychiatric problems and that surgically removing the white fibers connecting the frontal lobe with the rest of the brain will help mental health conditions. Moniz technique was later widely utilized in Europe and the United States. Moniz was awarded the Nobel Prize in 1949 for his contributions. In the United States, prefrontal leucotomy was initially used, but modified by an American neurosurgeon named Walter Freeman, who developed a transorbital leucotomy procedure. Unlike the original lobotomy that involved an open surgery, transorbital leucotomy was a minor surgery. It lasted about 10 to 20 minutes and aimed at separating the frontal lobe from the thalamus by accessing the brain through the back of the orbits with a sharp instrument similar to an ice pick. Clinicians often used this treatment even though, at the time, there was not much data to evaluate the effectiveness of this method, and because of the lack of alternative treatment for patients who had debilitating mental health problems. Later, retrospective studies showed that while Dr. Freeman's approach helped calmed some severely agitated patients, many ended up with numerous complications. In the late 1950s, pharmacotherapy was introduced and changed the approach in treating psychiatric conditions. Chlorpromazine was the first U.S. Food and Drug Administration approved psychotropic drug. While pharmacotherapy led to psychosurgery quietus, physicians laid the groundwork for the development of stereotactical microsurgery techniques. Speigel and Wycis developed the concept of stereotactic surgery to perform precise ablative lesions in deep areas of the brain in 1947. In 1962, Foltz and White used this technique for stereotactic anterior cingulotomy. Furthermore, the rapid development of numerous modalities helped to understand the structure and function of the brain. These new advances, coupled with the frustrations of the significant percentage of patients not responding to pharmacotherapy and positive results in the use of neuromodulation surgery like deep brain stimulation (DBS) in the treatment of movement disorders like Parkinson's disease, leaded clinicians to revisit the use of neuromodulation surgery for the treatment of psychiatric disorders. However, professionals debated whether these techniques will be used only as a last resort for the treatment of refractory psychiatric symptoms, or if they will be used for other purposes like to modify the cognition of healthy individuals.  Ethical requirements and guidelines for the procedures began to appear in physician's societies., (Copyright © 2022, StatPearls Publishing LLC.)

The presence of focal neurologic findings or mental status changes is predictive of complications following trauma. A neurologic examination helps to localize and lateralize lesions due to traumatic head or spine injury. The physical examination in the setting of significant trauma must be assessed rapidly, is individualized based on the patient's medical stability, combativeness, and type of injuries, and is often performed under chaotic circumstances. , (Copyright © 2022, StatPearls Publishing LLC.)

A subarachnoid hemorrhage (SAH) results from a medical aneurysmal rupture or traumatic head injury. SAH occurs in the subarachnoid space between the arachnoid membrane and the pia mater that surrounds the brain. Patients typically experience a "thunderclap-like" severe headache; however, only 10% of patients presenting to the emergency department with complaints of a headache end up having a SAH.  Other associated symptoms may include neck pain, nausea/vomiting, and photophobia. This is often a devastating clinical event with substantial mortality and high morbidity among survivors. , (Copyright © 2022, StatPearls Publishing LLC.)

The maxilla is the most important bone of the midface. It has a central location and provides structural support to the viscerocranium. It has functional and aesthetic significance as it has a fundamental role in facial architecture, separates the nasal and oral cavities, forms the upper jaw, and contains the maxillary sinus.[1][2], (Copyright © 2022, StatPearls Publishing LLC.)

Cerebellar hemorrhage or hematoma is a type of intracranial hemorrhage (ICH) where the bleeding is located in the posterior fossa or cerebellum and accounts for 9% to 10% of all ICH.[1] The posterior fossa is a small space in the skull containing the brainstem and cerebellum. If a mass such as a hemorrhage grows in this region, particularly the brainstem and 4th ventricle, it can block the normal flow of cerebral spinal fluid leading to hydrocephalus, increased intracranial pressure, and symptoms onset. Cerebellar hemorrhage can be spontaneous, a result of a stroke or secondary to trauma, and occurs most frequently in middle-aged and older adults. Patients typically have underlying risk factors leading to hemorrhages such as hypertension or small vessel disease. The clinical presentation is dependent upon the size and location of the hematoma as well as the location and amount of edema of associated structures in the posterior fossa. The initial imaging modality is typically a non-contrast computed tomography (CT) scan. Management spans the spectrum from close observation to acute surgical intervention with optimal timing of surgery., (Copyright © 2022, StatPearls Publishing LLC.)

Nevus flammeus or port-wine stain is a capillary malformation presenting as a pink or red patch on a newborn's skin. It is a congenital skin condition that can affect any part of the body and persists throughout life. It needs to be differentiated from a nevus simplex/salmon patch, which is usually seen along the midline and disappears over time. An acquired port-wine stain, clinically and histopathologically indistinguishable from congenital capillary malformation, has been reported to develop in adolescents or adults usually following trauma. Although nevus flammeus is a benign lesion, and often the diagnosis is clinical, occasionally detailed evaluation and radiological imaging are required when associated with other skin, soft tissue, skeletal, and vascular anomalies., (Copyright © 2022, StatPearls Publishing LLC.)

Rudolf Balint first described Balint syndrome in 1909. In his original observations, Balint described the patient's clinical symptoms, which included: 1. An inability to visualize more than one object in the visual field at a time (psychic paralysis of gaze or visual inattention). 2. An inability to identify different items in a visual scene simultaneously (a spatial disorder of attention or simultagnosia). 3. A failure to reach an object with his right hand but able to do so with the left hand. (Misreaching or optic ataxia). The patient had normal visual acuity, color vision, and intact extraocular muscle movements, and his autopsy revealed changes suggestive of chronic cerebrovascular disease in bilateral posterior parietal lobes. The postulation then was that the symptoms were from a lack of coordination between sensory input and motor output. In 1919, Holmes and Horrax described another case with a similar presentation, but the authors postulated that the patient’s inability to touch or point to objects was due to visual disturbances only. They considered that the patient had no trouble in performing sensory or motor tasks that did not need visual input, hence the primary deficit had to be in visual fields., (Copyright © 2022, StatPearls Publishing LLC.)

Venous sinus thromboses (VST) are venous blood clots of the major veins of the brain. They can be provoked or unprovoked, and the signs and symptoms thereof will depend on the location and extent of the clot. Common locations for sinus thrombosis include the dural sinuses, the cavernous sinus, and deep sinuses of the cortex., (Copyright © 2022, StatPearls Publishing LLC.)

Permissive hypotension, also commonly known as hypotensive resuscitation, is the method of non-aggressive fluid resuscitation in which volume repletion is limited in order to sustain a goal systolic or mean arterial pressure (MAP) below normal physiological conditions in the setting of volume loss. Such a technique is commonly employed in the trauma setting for patients experiencing acute hemorrhagic volume depletion. Various sources have outlined a decrease in mortality when blood pressures are adjusted below the normal physiologic range. Different sources have stated a quicker recovery and a decrease in postoperative recovery time when permissive hypotension is put into practice. This is, in contrast, to immediately normalizing an individual's blood pressure. Results, however, have not delineated a standard algorithmic approach to pressure stabilization in patients with different confounding factors such as age, pre-existing health conditions, and different methods of injury. Given such different methods of achieving permissive hypotension, the challenge of hypotensive resuscitation lies in how low one should set the limiting threshold for permissible hypotension with respect to a patient's age, demographics, and condition causing the acute volume depletion., (Copyright © 2022, StatPearls Publishing LLC.)

Decorticate posturing is a specific pattern of response shown in neurological and neurosurgical patients in whom the pathological processes have led to intracranial hypertension and already initiated the herniation syndrome. There will be flexor posturing along with internal rotation of the upper limbs with extensor posturing of the lower limbs. The painful stimulation should be given over supra eye-brow region or on other dermatomal distribution of cranial nerves only, to prevent the confounding bias from response seen from the spinal reflexes.[1][2] The internal rotation posturing helps to differentiate it from normal flexor response to pain., (Copyright © 2022, StatPearls Publishing LLC.)

Choroid plexus papillomas (CPPs) are rare central nervous system tumors. They may be seen at any age, but are more common in infants. Their site of occurrence varies according to age. They usually present with the increasing head circumference or altered mental status in children; whereas in adults they present with signs of increased intracranial tension. Imaging shows intraventricular enhancing masses. Surgery is the therapeutic intervention of choice for these lesions. They have a good prognosis in spite of their size as they are benign. Improvements in surgical techniques and intensive care have improved survival., (Copyright © 2022, StatPearls Publishing LLC.)

Kluver-Bucy syndrome (KBS) is a neuropsychiatric disorder due to lesions affecting bilateral temporal lobes, especially the hippocampus and amygdala.[1] The following clinical features characterize the syndrome: 1. Hyperorality. 2. Hypermetamorphosis (excessive attentiveness to visual stimuli with a tendency to touch every such stimulus). 3. Hypersexuality. 4. Bulimia. 5. Placidity. 6. Visual agnosia and 7. Amnesia. Patients having a combination of three or more different elements listed above are described as having partial KBS.[2][3] The clinical features of KBS were initially reported by Sanger Brown and Edward Albert Sharpey-Schäfer in 1888.[4] But the complete syndrome was described later by Heinrich Kluver (neuropsychologist) and Paul Bucy (neurosurgeon) in 1939, unaware of the previous reporting.[5] They described the behavioral syndrome which occurred in a Rhesus monkey (named Aurora) three weeks after bilateral temporal lobectomy. The first description of KBS in humans came from Dr. Terzian and Dr. Ore in 1955 in a 19-year-old man who underwent bilateral temporal lobectomy for seizures.[6] The first identified and reported case of KBS was in a 22-year-old male patient with bilateral temporal damage due to herpes simplex meningoencephalitis by Marlowe et al.[7], (Copyright © 2022, StatPearls Publishing LLC.)

The hypothalamus is a structure of the human brain that governs a wide range of physiological processes, including circadian rhythm, homeostasis, and stress response, as well as growth and development. Regulation of these activities is achieved, in part, via the activities of the hypothalamic-pituitary-adrenal axis (HPA). The supraoptic nucleus is a collection of magnocellular neurosecretory cells (MNCs) located within the anterior hypothalamus that participate in the HPA axis. The primary function of these cells is to produce and secrete the peptide hormone vasopressin, also known as antidiuretic hormone (ADH) and oxytocin. Vasopressin serves to maintain the body's osmotic balance and regulate the body's blood pressure by instigating aquaporin expression in the kidney's distal tubule and collecting duct to increase water absorption. Oxytocin is a neuropeptide that is well known for its importance in lactation and parturition.[1][2][3][4][5], (Copyright © 2022, StatPearls Publishing LLC.)

The two jugular foramina are openings in the skull base located on either side, anterolateral to the foramen magnum. The main structures which pass through this foramen are the glossopharyngeal (IX), vagus (X), and spinal accessory (XI) nerves and the internal jugular vein (IJV). The foramen is divided into two parts by a fibro-osseous bridge connecting the jugular spine of the temporal bone and jugular process of the occipital bone. The anteromedial compartment (pars nervosa) contains the cranial nerve IX, the tympanic branch of IX (Jacobson's nerve), and the inferior petrosal sinus. The posterolateral component (pars venosa or vascularis) contains the IJV, jugular bulb, cranial nerves X and XI, the auricular branch of vagus (Arnold's nerve), and the posterior meningeal branch of the ascending pharyngeal artery.[1] The jugular foramen syndrome (JFS or Vernet syndrome) refers to paralysis of the IX, X, and XI cranial nerves traversing the jugular foramen. Vernet first described it in the Paris Medical Journal (1917)., (Copyright © 2022, StatPearls Publishing LLC.)

To maintain a stable perception of the world around us while we engage in normal movements throughout our day, such as walking, we have something known as the vestibulo-ocular reflex (VOR). This reflex keeps us steady and balanced even though our eyes and head are continuously moving when we perform most actions. When we make a head movement, our eye muscles are triggered instantly to create an eye movement opposite to that of our head movement at the exact same speed to readjust the visual world, which, in turn, stabilizes our retinal image by keeping the eye still in space and focused on an object, despite the head motion., (Copyright © 2022, StatPearls Publishing LLC.)

Initially described by Kernohan in 1932, myxopapillary ependymoma is a distinct subtype of spinal cord ependymomas that has a predilection for the lumbosacral region.[1] It represents 13% of all spinal ependymomas and accounts for 90% of all tumors in the conus medullaris.[2][3] Myxopapillary ependymoma is a benign and slow-growing neoplasm that has been histologically classified as grade 2, according to the World Health Organization (WHO) classification., (Copyright © 2022, StatPearls Publishing LLC.)

Neurogenic pulmonary edema (NPE) is a clinical condition that arises as acute respiratory distress taking place in conjunction with severe neurological damage/injury. By definition, this condition incorporates a clinical picture of a large accumulation of extra-vascular pulmonary fluid, of acute onset, always in the immediate outcome of serious central nervous system (CNS) lesions, mostly the brainstem. Shanahan first described acute neurogenic pulmonary edema in 1908. This diagnosis necessitates the exclusion of other identifiable origins of pulmonary lesions or cardiovascular function that may accompany nervous system distress, for instance, broncho-pulmonary aspiration or ischemic, toxic or traumatic lesions of the heart and lungs. If the standard clinical presentation is explicit, the diagnosis should be assumed when acute pulmonary edema is associated with CNS injury in the absence of primary pulmonary or cardiovascular injury; however, some ambiguity continues, particularly since the literature does not present a full comprehension of exact pathogenesis., (Copyright © 2022, StatPearls Publishing LLC.)

Pneumocephalus (also known as pneumatocele or intracranial aerocele) is defined as the presence of air in the epidural, subdural, or subarachnoid space within the brain parenchyma or ventricular cavities. Lecat first described this condition in 1741, but the term "pneumocephalus" was coined independently by Luckett in 1913 and Wolff in 1914. The term "tension pneumocephalus" (TP) was proposed in 1962 by Ectors, Kessler, and Stern. Pneumocephalus can occur following trauma, cranial surgeries, or spontaneously. It is classified as simple or tension pneumocephalus. It can also be classified as acute (less than 72 hours) or delayed (72 hours or more). It has to be differentiated from the following terms: 1. Pneumorrhachis denotes intraspinal air. 2. Pneumocele is a focal or diffuse enlargement of any paranasal sinus (usually frontal) associated with thinning of its bony walls and hyperpneumatization. 3. Pneumosinus dilatans is the same as pneumocele, but the sinus walls are intact and normal. 4. Pneumoventricle is the presence of intraventricular air. The term tension pneumoventricle is used when there is an intraventricular accumulation of air causing an increase in the intracranial pressure and compression of vital centers., (Copyright © 2022, StatPearls Publishing LLC.)

Agenesis of corpus callosum (ACC) [OMIM 217990] is one of the most common congenital cerebral malformations which is morphologically the complete or partial absence of corpus callosum, and not defined by functional or behavioral abnormalities (as in autism). Corpus callosum is the largest white matter structure containing 200 million axons,[1] connecting the two hemispheres of the brain. Its formation starts by 74 days of gestation, with the first fibers crossing the midline at 11 to 12 weeks of gestation, development getting completed by 115 days and the basic shape assumed by 18 to 20 weeks of gestational age.[2] The formation is primarily from anterior to posterior, starting with the genu and finishing with the rostrum., (Copyright © 2022, StatPearls Publishing LLC.)

The natural history of a disease classifies into five stages: underlying, susceptible, subclinical, clinical, and recovery/disability/death. Corresponding preventive health measures have been grouped into similar stages to target the prevention of these stages of a disease. These preventive stages are primordial prevention, primary prevention, secondary prevention, and tertiary prevention. Combined, these strategies not only aim to prevent the onset of disease through risk reduction, but also downstream complications of a manifested disease., (Copyright © 2022, StatPearls Publishing LLC.)

The term os odontoideum (OO) refers to an anatomic anomaly of the upper cervical spine which was first described by Giacomini in 1886.[1] This condition is defined radiologically as an oval or round-shaped ossicle with smooth circumferential cortical margins representing a hypoplastic odontoid process (dens) that has no continuity with the C2 vertebral body.[2][3][4]  (See Figure) . The ossicle is usually cranially migrated relative to the expected position of the odontoid tip and can adopt two anatomic types (Fielding et al.): orthotopic (ossicle located in the position of the normal odontoid) and dystopic (ossicle located near the occiput in the area of the foramen magnum).[5][6][7] Researchers have described variable radiological sizes regarding OO. However, most present are half the size of a normal odontoid process, some are so small and cephalic that it may be hard to diagnose on plain X-rays or computed tomography (CT).[4] The ossicle is located slightly posterior and superior to the anterior arch of C1.[8] The OO is often attached to the anterior arch of C1 through an intact transverse ligament. One of the main risks of this anatomical entity is the association of anterior atlantoaxial subluxation. Posterior atlantoaxial subluxation is extremely rare.[9] This atlantoaxial instability can lead to cervical spinal stenosis with resultant cervical myelopathy due to vascular compromise, bony compression, and/or stretching of the spinal cord.[10], (Copyright © 2022, StatPearls Publishing LLC.)

Benign occipital seizures are classified as an occipital onset epilepsy syndrome, which occurs in children with normal developmental milestones, normal general and neurological examination, and without any structural abnormalities in the brain. These seizures are limited to childhood-onset only. Under the International league against epilepsy (ILAE) classification, this is classified under childhood epilepsy syndromes. These are rare conditions with a very low incidence; however, their exact incidence is unclear.[1] These epilepsies are broadly classified into 2 categories based on their clinical presentation. Children with Panayiotopoulos syndrome (PS) have autonomic symptoms, while children with idiopathic childhood occipital epilepsy of Gastaut (ICOE-G) have visual symptoms.[2][3] A small number of patients with this syndrome cannot be placed in either of these 2 categories.[4], (Copyright © 2022, StatPearls Publishing LLC.)

Locked-in syndrome (LIS) is a complex medical condition presenting with quadriplegia, bulbar palsy, and whole-body sensory loss due to damage in the brain stem, most commonly the anterior pons. Cognition, vertical eye movement, blinking, and hearing are classically preserved in patients suffering from the condition. The diagnosis of the locked-in syndrome is often challenging due to its similarity with conditions such as akinetic mutism and coma. It may take weeks to diagnose, and family members at the bedside are usually the first to notice the decreased motor functions of the patient.[1] Locked-in syndrome has three main types.[2] The classical form is defined by total immobility, with the preservation of the ability to perform vertical eye movements, blink, and maintain a normal level of consciousness. The incomplete form is defined as the classical form with small additional motor functions. The total immobility form is defined as a complete body paralysis, and loss of eye movement with the preservation of cortical function examined via EEG. In the classical and incomplete forms, consciousness is often evaluated by blink-response or eye movement-response to questions. An EEG may be used in patients in the complete form to assess brain activity, sleep-wake cycles, and attention.[3]  In the acute setting, CT or MRI of the brain helps characterize the causative agent to establish a treatment earlier. Physical examinations analyzing motor function, sensation, and reflexes are often reassessed to rule out other potential conditions and estimate the rate of recovery in patients.[4] Due to the rare nature of this condition, recovery and management have been a topic of debate. Still, an increasing amount of literature has demonstrated efficacy in traditional supportive management and rehabilitation., (Copyright © 2022, StatPearls Publishing LLC.)

Lissencephaly includes a range of severe brain malformations, including agyria (absent gyri), pachygyria (broad gyri), and subcortical band heterotopia.[1] In lissencephaly (which literally means smooth brain), the surface of the brain appears smooth.[2] It may occur as an isolated lissencephaly or in association with certain syndromes (Miller-Dieker syndrome).[3] Lissencephaly is caused by a defect in neuronal migration during embryonic development between 12 and 24 weeks of gestation that results in the absence of normal development of brain gyri and sulci.[4] Children with lissencephaly present with significant developmental delays and mental disability, but these vary from child to child depending on the degree of brain malformation and intractable epilepsy.[5], (Copyright © 2022, StatPearls Publishing LLC.)

Steppage gait is the inability to lift the foot while walking due to the weakness of muscles that cause dorsiflexion of the ankle joint. Foot drop is not a commonly seen condition. The typical presentation is one of a patient who presents with a sudden onset of weakness of the muscles that extend the foot during walking. The history usually consists of unusual activity, a surgical procedure, prolonged bed rest, an accident leading to fracture, or a tight cast applied to the lower extremity. The other possibilities include a history of collagen vascular diseases leading to nerve ischemia. Peripheral neuropathies, the most common cause being diabetes, can lead to unilateral or bilateral foot drop. Upper motor neuron lesions can also present as foot drop. However, the presentation also includes hemiplegia and aphasia., (Copyright © 2022, StatPearls Publishing LLC.)

The human vertebral column or spine has five distinct anatomical regions: cervical, thoracic, lumbar, sacral, and coccygeal. However, the cervical spine is a potential area of importance due to its proximity to the head, containment of the upper spinal cord, and vertebral arteries that contribute to the posterior circulation of the brain. Seven cervical vertebrae, combined with cartilages, various ligaments, and muscles, make a sophisticated and flexible structure that allows a variety of head/neck movements. Similar to other areas of the spine, cervical vertebrae also have intervening intervertebral disks for shock absorption and flexibility. Additionally, it contains a much wider spinal canal to accommodate the spinal cord, blood vessels, meninges, and nerve roots., (Copyright © 2022, StatPearls Publishing LLC.)

The human brain is unlike any organ, in that it receives a complex vascular supply through various significant arteries. This vascular supply may be broken down into the anterior and posterior circulations. The primary contributors to the anterior circulation of the brain are the internal carotid arteries (ICA), while the primary contributors to the posterior circulation are the vertebral arteries (VA). As the ICA traverses superiorly, it gives off important branches such as the posterior communicating artery (Pcom), anterior choroidal artery (AchA), anterior cerebral artery (ACA), and middle cerebral artery (MCA). Due to the presence of bilateral internal carotid arteries, these branches occur bilaterally and are a significant component of anastomosis of arteries in the base of the brain known as the circle of Willis. The circle of Willis permits collateral circulation throughout the cerebral cortex and thus allows compensation of flow when pathology such as embolus or aneurysm occurs. Even though the major branches of the ICA, such as the ACA and MCA supply entire hemispheres of the cerebral cortex, minor branches such as the AchA still play a crucial role in our daily function.  Although isolated involvement of the AchA is rare, it may suffer compromise by various pathologies such as brain infarctions, aneurysms, arterio-venous malformations, and brain tumors. , (Copyright © 2022, StatPearls Publishing LLC.)

Lasegue sign or straight leg raising test (SLRT) is a neurodynamic exam to assess nerve root irritation in the lumbosacral area.[1] It is an integral element to the neurological exam for patients presenting with low back pain with or without radicular pain. The other less commonly used name is Lazarevic sign., (Copyright © 2022, StatPearls Publishing LLC.)

Thalamocortical radiations are the nerve fibers between the thalamus and the cerebral cortex. Functionally, thalamocortical radiations, also called thalamocortical fibers, relay sensory or motor information from the thalamus to distinct areas of the cerebral cortex through relay neurons. Structurally, thalamocortical radiations are parallel pathways linking specific thalamic nuclei with specific cortical areas. There are also corticothalamic fibers, which relay information back to the thalamus from the cerebral cortex. Thalamocortical radiations are involved in the control of cortical arousal and consciousness, and play a role in movement disorders such as Parkinson disease., (Copyright © 2022, StatPearls Publishing LLC.)

Esthesioneuroblastoma, or olfactory neuroblastoma, is a rare malignant neoplasm of the sinonasal tract originating from the olfactory neuroepithelium with neuroblastic differentiation. It most often presents in the superior nasal cavity. Since its initial description in 1924 by Berger and Luc, there have been reports of more than 1000 cases of esthesioneuroblastoma worldwide.[1] Esthesioneuroblastoma is a locally aggressive neoplasm and metastasizes by both hematogenous and lymphatic routes., (Copyright © 2022, StatPearls Publishing LLC.)

The septum pellucidum (meaning translucent wall in Latin - SP), also known as the ventricle of Sylvius, is a thin, triangular double membrane separating the frontal horns of the right and left lateral ventricles of the brain. It extends between the anterior portion of the corpus callosum, and the body of the fornix and its width varies from 1.5 to 3.0 mm  The cavum septum pellucidum (CSP) is a potential cavity between the membranous leaves of the septum pellucidum, separated by at least 1 mm, and is considered a normal anatomical variation. It contains a filtrate of cerebrospinal fluid transferred from the ventricles through the septal laminae, and it does not communicate with the subarachnoid space. Sometimes, it may connect to a more posterior cavity called cavum vergae (CV), but separates from each other by an arbitrary vertical plane formed by the columns of the fornix. CSP and CV were respectively and incorrectly called the fifth and sixth ventricles in the past. Both are not parts of the ventricular system as they have a different embryological origin and lack a lining with ependymal or choroid plexus cells. Boundaries of SP: Superiorly - Inferior surface of the body of the corpus callosum Antero-inferiorly - Superior surface of the genu of the corpus callosum Posteroinferiorly - Corpus and columns of the fornix Laterally - Medial wall of frontal horns of lateral ventricles Medially - Virtual space with the contralateral septum Boundaries of CSP [1] Anteriorly - Genu of the corpus callosum Superiorly - Body of the corpus callosum Posteriorly - Anterior limb and pillars of the fornix Inferiorly - Anterior commissure and the rostrum of the corpus callosum and Laterally - Leaflets of the septum pellucidum. SP is an important part of the limbic system, with prominent connections to both the medial and the basolateral limbic circuit. Disease affecting the CSP can cause symptoms either by mass effect or by disturbance of the emotional and behavioral functions of the limbic system., (Copyright © 2022, StatPearls Publishing LLC.)

Cortical blindness is among the rare neurological conditions resulting in binocular vision loss due to insult to the occipital cortex. Anton-Babinski syndrome (Anton syndrome or ABS) is visual anosognosia (denial of loss of vision) associated with confabulation (defined as the emergence of memories of events and experiences which never took place) in the setting of obvious visual loss and cortical blindness. It is essentially neurological visual impairment/disturbance resulting from abnormality or damage in the brain rather than due to eye abnormalities.  The first description of ABS dates back to the Roman era when Seneca, a Roman philosopher and politician, described the case of Harpaste, a slave who acutely became blind. She used to deny her illness and argue irrationally about room darkness and constantly ask her attendants to change quarters. This case demonstrates the main symptoms of ABS, including acutely acquired blindness and anosognosia in the presence of relatively well-preserved cognition. The next documented description of visual anosognosia was made by the French Renaissance writer Michel de Montaigne (1533 - 1592), who described a nobleman who denied his blindness. In 1895, the Austrian psychiatrist and neurologist Gabriel Anton (1858 - 1933) described the case of Juliane Hochriehser, a 69-year-old dairymaid who had anosognosia with cortical deafness due to a lesion on her both temporal lobes. He also outlined other cases of patients with objective blindness and deafness who denied their deficits. In 1914, the French-Polish neurologist Joseph François Babinski (1857 - 1932) used for the first time the term “anosognosia” to describe the unawareness of the deficit in patients with hemiplegia. In 1920 Meyer first reported occipital lobe infarction and postulated compression of branches of the posterior cerebral artery as the causal factor for ABS., (Copyright © 2022, StatPearls Publishing LLC.)

Ilioinguinal neuralgia is a frequent cause of pain in the lower abdomen and the upper thigh. The ilioinguinal nerve is a mixed nerve originating from the anterior rami of T12 and L1 nerve roots. It emerges near the lateral border of the psoas major muscle and goes inferior through the anterior abdominal wall, being sub-peritoneal and anterior to the quadratus lumborum muscle until it reaches the iliac crest. Then the ilioinguinal nerve goes through the transverse abdominis and the internal oblique muscles. It becomes superficial by passing through the superficial inguinal ring anterior to the spermatic cord. It gives motor innervation to the transverse abdominis and the internal oblique muscles. Also, it carries sensory information from the anterior surface of the scrotum and root of the penis in males or labia majora and mons pubis in females, and a small area of the upper anteromedial thigh. Because of its long course, entrapment or injury of the nerve after lower abdomen surgeries is common. Male or female patients can complain of pain, paresthesia, and abnormal sensation in the area supplied by the nerve. Diagnosis of ilioinguinal neuralgia requires a careful history, physical examination, electrophysiologic studies, and ultrasound examination. Treatment of the ilioinguinal neuralgia includes conservative measures as oral analgesics, anticonvulsants, rehabilitation as electro-analgesic currents, and myofascial release. If conservative measures do not control symptoms, ultrasound-guided block, hydro-dissection, or radio-frequency ablation of the nerve can provide satisfactory symptomatic relief. Resistant cases may require neurectomy.[1][2][3], (Copyright © 2022, StatPearls Publishing LLC.)

The glossopharyngeal nerve is the 9th cranial nerve (CN IX). It is one of the four cranial nerves that has sensory, motor, and parasympathetic functions. It originates from the medulla oblongata and terminates in the pharynx. This nerve is most clinically relevant in the setting of glossopharyngeal neuralgia, but an injury to it can also be a complication of carotid endarterectomy., (Copyright © 2022, StatPearls Publishing LLC.)

The Red Nucleus (RN) is a primitive brainstem structure located in the ventral midbrain. Histologically, the RN consists of two distinct structures: a caudal parvocellular red nucleus (RNp) and a rostral magnocellular red nucleus (RNm).[1][2] Although the origin of the RN is not completely understood, studies suggest it can be attributed to the evolutionary development of limbs and locomotion among vertebrates.[3] Specifically, when comparing different species, there is wide variability in both the structure and function of the RN. Generally speaking, the RNm predominates in lower vertebrates, while the RNp is more prominent in higher species.[2] With regards to quadrupedal mammals (i.e., cats and rats), the RNm is highly developed. However, when progressing upward the evolutionary pyramid, the RNm decreases in size and ultimately bares minimal significant volume or neurological function within the human brain (conversely, the RNp occupies most of the RN total volume in humans).[1][4][5][6] Furthermore, although the two subsections of the RN are virtually undifferentiated in lower mammals, the human RNm and RNp are so distinct that they are more so considered two completely independent structures altogether.[2], (Copyright © 2022, StatPearls Publishing LLC.)

Weber's syndrome was described first by the German-born English physician Hermann Weber in a 52-year-old male who had developed left-sided third nerve palsy with right-sided hemiplegia caused by an acute bleed in the left cerebral peduncle. Weber syndrome, classically described as a midbrain stroke syndrome and superior alternating hemiplegia, involves oculomotor fascicles in the interpeduncular cisterns and cerebral peduncle, thereby causing ipsilateral third nerve palsy with contralateral hemiparesis. It most commonly results from the occlusion of a branch of the posterior cerebral artery. The oculomotor(third cranial) nerve has two main motor nuclei, the main motor nucleus, and the accessory parasympathetic nucleus. The main motor nucleus is located in the tectum portion of the midbrain at the level of the superior colliculus and supplies all the extraocular muscles except the lateral rectus and the superior oblique muscles, and the levator palpebrae superioris. The accessory parasympathetic nucleus, also known as the Edinger Westphal nucleus, is situated posterior to the main motor nucleus and its postganglionic fibers pass through the short ciliary nerves to supply the constrictor pupillae of the iris and the ciliary muscles. The nerve fascicles then travel forward and lateral through the red nucleus and converge at the interpeduncular fossa before exiting the midbrain. As the nucleus and fascicles are spread over a large area of the midbrain, lesions in the midbrain can present with either partial or complete third nerve palsy. The lesions in lower midbrain affect the extraocular muscles but spare the pupils, while lesions affecting both upper and middle parts of the midbrain are associated with pupillary dilatation. , (Copyright © 2022, StatPearls Publishing LLC.)