Hypertrophic olivary degeneration : Cause of new neurological symptoms after stroke

Abstract

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 arhythmic palatal tremor, aprimarily vertical pendular nystagmus as well as Holmes' tremor of the upper limbs. 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. The neuroradiological database of the Goethe University Hospital was screened for HOD and related keywords (in German). Between 2010 and 2017 atotal of 27cases of HOD were identified, of which 12patients had suffered astroke in their medical history. The mean age of the 12patients was 51.4years (±13.6years) 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 24months (min.4months, max. 115months). 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. 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.