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Background: Hypertrophic olivary degeneration (HOD) occurs as a result of a lesion in the anatomical functional loop of the Guillain-Mollaret triangle. Frequent causes are intracerebral hemorrhage and brain infarction. After a latent period of weeks to months after the index event a hyperintensity can initially be observed in magnetic resonance imaging T2/FLAIR-weighting and finally an enlargement of the affected olive. Characteristic symptoms are a rhythmic palatal tremor, a primarily vertical pendular nystagmus as well as Holmes' tremor of the upper limbs., Aim of the Study: The goal of this study was to illustrate the course of the disease and its clinical presentation in order to provide an improved understanding of the pathophysiology of HOD after stroke., Material and Methods: The neuroradiological database of the Goethe University Hospital was screened for HOD and related keywords (in German). Between 2010 and 2017 a total of 27 cases of HOD were identified, of which 12 patients had suffered a stroke in their medical history., Results: The mean age of the 12 patients was 51.4 years (±13.6 years) and one third of the patients were women. Of the patients eight had an intracerebral hemorrhage, three an ischemic stroke and one had a subarachnoid hemorrhage as the causative event. The lesions were located in the pons (n = 7), cerebellum (n = 4) and pontomesencephalon (n = 1). The median latent period from the causative index event to radiological diagnosis was 24 months (min. 4 months, max. 115 months). The leading symptoms of HOD were palatal tremor (55%), Holmes' tremor (18%), pendular nystagmus (18%) and dysarthria (73%). A logopedic examination with flexible endoscopic evaluation of swallowing (FEES) could determine a palatal tremor in five out of nine cases. The diagnosis of HOD was named in the medical report in only 50% of the cases., Conclusion: Analysis of the dataset provided confirmation of the results in the literature that lesions within the Guillain-Mollaret triangle more often lead to HOD. Patients with corresponding symptoms should be closely observed over time with respect to the occurrence of corresponding clinical and imaging leading symptoms. Even though the named clinical symptoms are characteristic for HOD, in many cases the diagnosis is hampered and delayed by imprecise examination and misinterpretation of the symptoms. A logopedic examination using FEES in this collective often provided indicative information. Currently, no reliable data are available on the incidence of HOD after brainstem lesions or on potential preventive and treatment options. Future epidemiological and translational studies could perspectively enable valuable insights to be gained.

Competing Interests: Alle Autoren erklären hiermit, dass die Erstellung dieser Arbeit unabhängig von materiellen Interessen erfolgte und die Darstellung der Inhalte produktneutral gehalten sind.

Hirayama disease is a juvenile benign distal upper limb muscular atrophy rarely observed in Europe, usually monomelic involving C7-Th1 innervated muscles. It is characterized by insidious onset and a self-limited course within a few years. The pathogenesis of this mostly sporadic disease is not fully clarified. Cervical flexion myelopathy with mechanical ischemic damage of spinal motoneurons is the best established pathogenetic hypothesis, but neurodegenerative and autoimmune causes are also debated. Typically, young men of Asian origin are affected. Here we describe three German Caucasian patients with Hirayama disease and provide an up-to-date review of the literature.