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This case report describes the clinical journey of a male patient in early childhood with developmental delay, failure to thrive, worsening right-sided head tilt torticollis and regression of motor skills with spasticity of the lower limbs. The case was complex due to the early onset and gradually worsening symptoms, including a decline in established motor milestones. Genetic testing to investigate the delayed neurodevelopment revealed a FRA10AC1 variant that did not fully explain the patient's phenotype. Investigations were delayed due to the coronavirus disease 2019 pandemic and other factors related to the patient. Eventually, MRI revealed basilar invagination with cord compression and cord oedema at the C1-C2 junction. Treatment included foramen magnum decompression and management of symptoms using a multidisciplinary approach. Treatment resulted in a remarkable recovery. The patient regained some motor abilities and reached the 50th weight percentile., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: The mechanisms of pendular seesaw nystagmus (SSN) remain unknown., Methods: We evaluated modulation of pendular SSN by removal of visual fixation, convergence, and positional changes in 2 patients, one with bitemporal hemianopia due to a traumatic damage of the optic chiasm and the other with platybasia compressing the medulla and lower cerebellum., Results: In both patients, the pendular SSN markedly decreased or disappeared with convergence, without visual fixation in darkness, during static head tilt toward each shoulder while sitting and while supine., Conclusions: The similar patterns of nystagmus modulation observed in our patients with a different etiology indicate a common role of both visual and otolithic inputs in generating pendular SSN.

A teenage girl presented with progressively worsening neck and occipital pain since 8 months ago that was associated with restriction of neck movements, low to moderate grade fever, anorexia and weight loss followed by gradually progressive quadriparesis since 3 months ago. Neurological examination revealed spastic quadriparesis without cranial nerve palsy. MRI of the cervical spine revealed prevertebral and paravertebral abscess from clivus to C2/C3 level, which extended into the anterior epidural space at C1-C3 level, causing atlantoaxial dislocation. There was evidence of basilar invagination. The dislocated dens caused compression over the cervicomedullary junction. On this basis, a diagnosis of craniovertebral junction Pott's disease was made. The patient was given neck immobilisation with cervical collar, and antitubercular treatment was started. She showed significant improvement in her neurological deficit during follow-up.

A case is presented of a 35-year-old woman diagnosed with platybasia associated with Klippel-Feil syndrome type I. She was admitted to University Department of Neurology for clinical examination because of walking difficulties, dizziness, and intermittent vision disturbances. Neurological examination revealed a predominance of cerebellar symptomatology. Relevant diagnostic work-up included craniogram, cervical spine x-ray, computed tomography (CT) of the brain and craniocervical junction, magnetic resonance imaging of the brain, electroencephalography, ophthalmologic examination, urinary tract ultrasonography, laboratory tests, and psychological testing. CT of the craniocervical junction showed platybasia, congenital fusion of the second and third cervical vertebrae, and basilar invagination of dens axis. Platybasia is leveling of the angle between the floor of the anterior cranial fossa and posterior cranial fossa in the area of sella turcica, which is normally at 115-140 degrees. Basilar impression or invagination is moving up of the basis of the occiput and occipital condyles into the cranium, which means that the borders of the foramen magnum, condyles and adjacent bone are invaginated into the posterior fossa. Klippel-Feil syndrome type II is massive fusion of two of seven cervical vertebrae associated with short neck and low hair line.

A 27-year-old woman presented with bilateral weakness of her all extremities for 5 years. She had a spastic gait and was unable to ambulate without assistance. Neurologic examination revealed increased deep tendon reflexes and positive pathologic reflexes. Radiographs showed occipitalization of the atlas, C2-C3 congenital fusion and fixed atlantoaxial dislocation with an atlanto-dental interval of 10 mm. MRI demonstrated cervicomedullary junction (CMJ) compression from the odontoid, a Chiari type I malformation, and syringomyelia extending from the foramen magnum to C5. The patient underwent transoral atlantoaxial release followed by posterior internal fixation from the occiput to the axis, which resulted in a significant improvement in motor function in all extremities. Post-operative images showed anatomical reduction of the atlantoaxial joint. However, an MRI performed 8 days following surgery showed a new retro-odontoid pannus had developed that was compressing the spinal cord at CMJ. A follow-up CT scan performed at 6 months post-operatively demonstrated a solid bony fusion between the occiput and C2, while an MRI at that time showed complete resolution of the retro-odontoid soft tissue mass with correction of the Chiari I malformation, and resolution of the syringomyelia. Final follow-up at 2-years revealed an excellent clinical outcome.

Institute and personal experience (over 25 years) of basilar invagination was reviewed. The database of the department included 3300 patients with craniovertebral junction pathology from the year 1951 till date. Patients with basilar invagination were categorized into two groups based on the presence (Group A) or absence (Group B) of clinical and radiological evidence of instability of the craniovertebral junction. Standard radiological parameters described by Chamberlain were used to assess the instability of the craniovertebral junction. The pathogenesis and clinical features in patients with Group A basilar invagination appeared to be related to mechanical instability, whereas it appeared to be secondary to embryonic dysgenesis in patients with Group B basilar invagination. Treatment by facetal distraction and direct lateral mass fixation can result in restoration of craniovertebral and cervical alignment in patients with Group A basilar invagination. Such a treatment can circumvent the need for transoral or posterior fossa decompression surgery. Foramen magnum bone decompression appears to be a rational surgical treatment for patients having Group B basilar invagination. The division of patients with basilar invagination on the basis of presence or absence of instability provides insight into the pathogenesis of the anomaly and a basis for rational surgical treatment.

We report on a 48 years-old man with basilar impression without syringohydromyelia, in which the cisterna magna was impacted by the cerebellar tonsils. Six months after posterior fossa decompression there was the disappearance of nuchal rigidity, vertigo, spastic paraparesis and improvement of balance. Nevertheless hyperreflexia and diminished pallesthesia of the lower limbs persisted.

Two patients presented with congenital basilar invagination manifesting as progressive myelopathy. Both patients underwent surgery using a neuronavigation-assisted transoral-transpharyngeal approach. The Brain-LAB Vector Vision navigation system was used for image guidance. The registration accuracies were 0.9 and 1.3 mm. After decompression, posterior stabilization was performed. Both patients had an uneventful postoperative course. The transoral-transpharyngeal approach with the neuronavigation system provides safe exposure and decompression for basilar invagination.

Purpose: To confirm the accuracy of the standard parameters of Chamberlain's line, McGregor's line, McRae's line, and Ranawat's line in the diagnosis of basilar impression in a normal Asian population using magnetic resonance imaging (MRI) scans of the craniocervical junction, and to evaluate the use of MRI in the initial diagnosis of basilar impression., Methods: We retrospectively reviewed MRI scans of the craniocervical junction in 114 Thai patients (61 men and 53 women) aged 20 to 89 years to assess the lines of Chamberlain, McGregor, McRae, and Ranawat. Patients with injury, tumour, or metastasis in the craniocervial junction; congenital anomalies; or clinical symptoms and signs of basilar impression were excluded., Results: 39 of the 114 patients had the odontoid tip extended above Chamberlain's line by 1 mm to 9 mm (mean, 2.89 mm). Only 7 men and 5 women had the tip of the odontoid process extended beyond the normal range of 5 mm. The mean distance of the odontoid tip extended past McGregor's line in male and female subjects was 0.33 mm (standard deviation [SD], 1.2 mm) and 0.17 mm (SD, 0.7 mm), respectively, markedly less than those reported previously, although one male patient's odontoid tip extended 8 mm above the McGregor's line. Regarding McRae's line, no patient had the odontoid tip extended above the foremen magnum. The mean Ranawat's line in male and female subjects was 15.75 mm (range, 12-19; SD, 1.71 mm) and 14.09 mm (range, 11-17; SD, 1.38 mm), respectively., Conclusion: After using MRI to confirm the standard parameters of basilar impression as previously formulated from lateral skull radiographs, we recommend using McRae's line and Ranawat's line in the initial screening for basilar impression for the Asian population. Chamberlain's line and McGregor's line are viable alternatives, but clinicians must be aware of the potential for false positives.

Background and Purpose: Platybasia, or abnormal obtuseness of the basal angle, was first measured on plain skull images. At present, evaluation of the brain and skull more commonly involves CT and MR imaging. We evaluated a new MR imaging method of evaluating platybasia., Methods: We retrospectively evaluated midline sagittal MR images in 200 adults and 50 children. The basal angle of the skull base was measured by using two methods: The standard MR imaging technique measured the angle formed by two lines-one joining the nasion and the center of the pituitary fossa connected by a line joining the anterior border of the foramen magnum and center of the pituitary fossa. The modified technique measured the angle formed by a line across the anterior cranial fossa and dorsum sellae connecting a line along the clivus., Results: With the standard MR imaging technique, we obtained mean angles of 129 degrees +/- 6 degrees for adults and 127 degrees +/- 5 degrees for children, compared with 135.3 degrees (composite mean) in previous series. The modified technique produced values of 117 degrees +/- 6 degrees for adults and 114 degrees +/- 5 degrees for children, which were significantly lower that those of standard MR imaging and traditional radiography (P <.05)., Conclusion: Both the standard and modified MR imaging techniques produced basal angles lower than those previously reported with standard radiography. The modified technique uses clearly featured landmarks that can be reproduced consistently on midline sagittal T1 images. This technique and its corresponding values can be used as the new standard for evaluating the basal angle.

We analyze the results of surgical treatment of 60 patients presenting syringomyelia (SM) associated with Chiari malformation (CM) who were operated in the period 1982-2000. For each case, analysis covered 15 signs and 16 symptoms included in a protocol that separated SM signs and symptoms from those of CM. A score system was established in parallel with the protocol to make the evaluation of treatment results easier. All cases were submitted to craniovertebral decompression by C1 and eventually C2 laminectomy and cerebellar tonsillectomy with duramater graft. To evaluate the results, statistical proportion difference tests and variance analyses were made to a reliability index of 95% (p=0.05). We conclude that the statistical improvement of CM signs and symptoms was very significant (p=0). Syringomyelia signs and symptoms also improved significantly, except for "upper limb hyporeflexia", which did not improve. No statistical difference in the improvement of SM symptoms as compared to CM symptom was found. Syringomyelia signs improved statistically more than CM signs. In half of patients, the percent improvement of signs and symptoms ranged between 40% and 60%.

Schwartz-Jampel syndrome is a rare, inherited disorder characterized by myotonia, skeletal deformities, facial dysmorphism, and growth retardation. In this report of an adolescent male patient with Schwartz-Jampel syndrome, CT and MR imaging revealed basilar invagination, platybasia, Chiari I malformation, hyperpneumatized mastoids with intramastoid dural sinuses, platyspondyly, bulbous zygoma, and blunted pterygoid processes.

Object: The authors analyzed the cases of 163 patients with syringomyelia to assess the appropriate surgical procedure., Methods: Depending on the aetiological factors and treatment considerations the series was classified into three groups. Group I were cases where there was no definite demonstrable aetiological factor; Group II cases had basilar invagination and/or Chiari malformation; and Group III consisted of cases where the syrinx was secondary to an obvious aetiology, such as a mass lesion either in the posterior cranial fossa or in the spine or a severe kyphotic spinal deformity. Post-traumatic syringomyelia and syrinx in association with spina bifida were not studied., Conclusions: We concluded that for Group I cases syringosubarachnoid shunting is the ideal form of treatment. In Group II cases foramen magnum bony decompression is satisfactory and physiological. Good results were obtained even in cases where either a foramen magnum decompression alone or in combination with a syringo-subarachnoid shunt was done. Only syringosubarachnoid shunt (without a foramen magnum decompression) in Group II cases was found to produce poor outcome. Group III cases should be treated for the primary aetiological problem. Only syrinx drainage procedure without treatment of aetiology in these cases produced poor results. It was observed that clinical outcome rather than radiological improvement is the reliable indicator of the surgical result.

A 47-year-old male presented with abducens nerve palsy due to basilar impression associated with atlanto-occipital assimilation manifesting as slowly progressive bilateral trigeminal neuralgia and diplopia in the right lateral gaze. X-ray and computed tomography of the skull confirmed the diagnosis of basilar impression and atlanto-occipital assimilation, and magnetic resonance imaging disclosed tightness of the posterior cranial fossa. Surgical suboccipital decompression resulted in gradual resolution of the patient's complaints, and no additional symptoms were recognized. Impairment of the sixth cranial nerve is a rare symptom compared to those of the fifth or the eighth cranial nerve in a patient with a craniocervical malformation. However, the present case shows the possibility of cranial nerve dysfunction due to tightness of the posterior cranial fossa, and suggests that surgical treatment for basilar impression with atlanto-occipital assimilation should be considered in patients with uncommon and unusual symptoms.

A 43-year-old woman presented with dull headache, left tinnitus and dizziness. Neurological examination revealed down-beat gaze nystagmus, left tinnitus, positive Romberg sign, poor standing on the left foot, poor tandem gait, left spastic gait and positive pathological reflexes in the bilateral upper and lower extremities. Plain X-ray of the skull and cervical vertebrae demonstrated basilar impression and atlantoaxial fusion. Magnetic resonance imaging of the brain and cervical spine showed cerebellar tonsil descent and syringomyelia located in the left side of the spine at the II-III vertebral level which communicated with the fourth ventricle. The patient was diagnosed as having cervical syringomyelia. Arnold-Chiari type I malformation and basilar impression. Preoperative polysomnography showed dysrhythmic breathing and bradypnea during sleep. Abnormal breathing improved after suboccipital decompression craniotomy and upper cervical laminectomy. It was suggested that dysrhythmic breathing was caused by a disorder of the medullary respiratory center. Herniation of the cerebellar tonsil and syringomyelia might have compressed the medulla.

Chamberlain's, McGregor's and Bull's angle measurements for basilar impression of the skull were made on 22 adult patients with idiopathic steatorrhoea (probable gluten enteropathy), 24 patients who had had previous gastric surgery, and 48 control subjects. For each of the three measurements a value greater than the mean plus two standard deviations was taken as the upper limit of normal. In seven patients with adult steatorrhoea all three measurements were abnormal suggesting basilar impression, while basilar impression was probable in only one patient who had gastric surgery. The trend towards abnormal measurements was significant in the steatorrhoea patients but not in those who had gastric surgery. Basilar impression also was present in patients who did not have rickets or present evidence of osteomalacia. It was argued that this study could support a hypothesis that some cases of primary basilar impression of the skull are secondary to bone softening associated with malabsorption in early life, the evidence of which may have disappeared in adult life.