Central Positional Vertigo and Nystagmus in a Posterior Fossa Tumor

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: This is a 30-year old woman who presented with positional vertigo and vomiting following a concussion related to a car accident 3 months prior. She was initially diagnosed with posterior canal (PC) benign paroxysmal positional vertigo (BPPV), although there was no improvement with Epley maneuvers. There was a history of migraine headaches, although the frequency of headaches did not increase following her mild concussion. General neurologic exam including evaluation of gait was normal. On ocular motor examination, there was no spontaneous nystagmus, and smooth pursuit, vestibulo-ocular reflex suppression, saccades and head impulse test were normal. There was only mild gaze-evoked nystagmus laterally - e.g., in right gaze, right-beating nystagmus is apparent, and in left gaze, left-beating nystagmus is apparent - without rebound nystagmus. Examination with video Frenzel goggles and removal of fixation demonstrated the following: when upright, there was no nystagmus; in bow (head flexed forward), there was down- and right-beating nystagmus (RBN); in lean (head extended back) there was upbeat- and left-beating nystagmus (LBN); when supine, there was initially RBN, which transitioned slowly to upbeat nystagmus and finally LBN; in right supine roll test (head rotated 90 degrees to the right with head slightly flexed) there was initially LB apogeotropic nystagmus (i.e., beating away from the earth) that slowed over seconds and transitioned to RBN; and in left supine roll test (head rotated 90 degrees to the left), there was initially RB apogeotropic nystagmus that slowed and gradually transitioned to LBN (the video cuts off before this can be seen). Two weeks after this examination, the patient returned with improved positional vertigo, although intermittent vomiting continued. MRI was obtained, which demonstrated a tumor originating in the 4th ventricle. The MRI appearance (T2 axial and sagittal views are included in the video) was most consistent with a subependymoma, and surgery is pending at this time. With PC BPPV, the Dix-Hallpike (DH) maneuver will trigger upbeat-torsional (top poles towards the lowermost, affected ear - see example https://collections.lib.utah.edu/ark:/87278/s6s79d1w). While the video does not include DH, this pattern of nystagmus was not triggered in the patient. With horizontal canal (HC) BPPV, pure horizontal nystagmus is triggered by supine roll test (and usually is seen to a lesser degree with DH as well). There are two HC BPPV variants - geotropic (beating toward the earth - see example https://collections.lib.utah.edu/ark:/87278/s6wx1fd1) and apogeotropic (beating away from the earth - see example https://collections.lib.utah.edu/ark:/87278/s61p1xt1). However, central etiologies can cause these patterns as well, more commonly apogeotropic pattern geotropic pattern. When positional vertigo and nystagmus are caused by a central lesion, apogeotropic positional nystagmus is usually related to pathology involving the nodulus/uvula,1 geotropic positional nystagmus is usually related to pathology involving the paraflocculus (tonsil),(2) and positional downbeat nystagmus is often caused by bilateral flocclus impairment.3 Central apogeotropic nystagmus is much more common than central geotropic nystagmus. Other ocular motor abnormalities are almost always present (e.g., saccadic dysmetria, impaired smooth pursuit, gaze-evoked nystagmus), and/or general neurologic or gait assessment is abnormal (e.g., ataxia). Rarely, the central positional nystagmus and vertigo occur in isolation. In this particular case, neuroimaging was indicated due to the following red flags: 1); The nystagmus was not in the plane of a particular semicircular canal and changed unpredictably with various head position (e.g., bow and lean caused down- and upbeat nystagmus, respectively); 2) The typical crescendo-decrescendo pattern of upbeat-torsional nystagmus triggered by Dix-Hallpike, which would suggest PC BPPV (the most common type of BPPV, especially common following head trauma), was lacking 3); Repeated, properly performed Epley maneuvers (treatment for PC BPPV) did not resolve the symptoms or nystagmus; 4); Vomiting persisted even as positional vertigo improved; 5); Mild gaze-evoked nystagmus was present laterally (regardless of the otherwise normal neurologic exam), which suggests dysfunction of the neural integrators - nucleus prepositus hypoglossi-medial vestibular nucleus complex or its connections with the cerebellar flocculus/paraflocculus; 6); While there was apogeotropic nystagmus with supine roll test, which could suggest HC BPPV, the nystagmus occurred without a clear latency, and quickly transitioned to nystagmus in the opposite direction; a. Furthermore, when apogeotropic HC BPPV is present, the direction of nystagmus changes with bow and lean, and this can be predicted based on knowledge of the involved side - e.g., in right apogeotropic HC BPPV, there may be pseudo-spontaneous nystagmus when upright that is RB (ipsilesional) nystagmus, and this will increase (RBN) in lean (head back), and transition to LB (contralesional) nystagmus in bow (head forward). See example - https://collections.lib.utah.edu/ark:/87278/s68h2wk9 The mechanism for central positional apogeotropic nystagmus may relate to impaired ability of the vestibulocerebellum (mainly nodulus/uvula) to accurately estimate the direction of gravity due to abnormal otolithic (utricular) inputs. This can result in a directional error away from true earth vertical, and this bias is thought to cause erroneous head rotation signals that lead to pathological nystagmus.(1) 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: This patient presented with positional dizziness and nystagmus, and examination with video Frenzel goggles and removal of fixation demonstrated the following: when upright, there was no nystagmus; in bow (head flexed forward), there was down- and right-beating nystagmus (RBN); in lean (head extended back) there was upbeat- and left-beating nystagmus (LBN); when supine, there was initially RBN, which transitioned slowly to upbeat nystagmus and finally LBN; in right supine roll test (head rotated 90 degrees to the right with head slightly flexed) there was initially LB apogeotropic nystagmus (i.e., beating away from the earth) that slowed over seconds and transitioned to RBN; and in left supine roll test (head rotated 90 degrees to the left), there was initially RB apogeotropic nystagmus that slowed and gradually transitioned to LBN (the video cuts off before this can be seen). MRI was obtained, which demonstrated a tumor originating in the fourth ventricle, which was eventually diagnosed as a subependymoma. When positional vertigo and nystagmus are central in origin, apogeotropic positional nystagmus is usually related to pathology involving the nodulus/uvula, geotropic positional nystagmus is usually related to pathology involving the paraflocculus (tonsil), and positional downbeat nystagmus is often caused by bilateral flocculus impairment. Central apogeotropic nystagmus is much more common than central geotropic nystagmus. Other ocular motor abnormalities are usually present and/or there is gait imbalance, but rarely central positional nystagmus/ vertigo occurs in isolation. In this particular case, neuroimaging was indicated due to the following red flags: (1) The nystagmus was not in the plane of a particular semicircular canal and changed unpredictably with various head position (e.g., bow and lean caused down- and upbeat nystagmus, respectively); (2) The typical crescendo-decrescendo pattern of upbeat-torsional nystagmus triggered by Dix-Hallpike, which would suggest PC BPPV (the most common type of BPPV, especially common following head trauma), was lacking; (3) Repeated, properly performed Epley maneuvers (treatment for PC BPPV) did not resolve the symptoms or nystagmus; (4) Vomiting persisted even as positional vertigo improved; (5) Mild gaze-evoked nystagmus was present laterally (regardless of the otherwise normal neurologic exam), which suggests dysfunction of the neural integrators-nucleus prepositus hypoglossi-medial vestibular nucleus complex or its connections with the cerebellar flocculus/paraflocculus; (6) While there was apogeotropic nystagmus with supine roll test, which could suggest HC BPPV, the nystagmus occurred without a clear latency, and quickly transitioned to nystagmus in the opposite direction. The mechanism for central positional apogeotropic nystagmus may relate to impaired ability of the vestibulocerebellum (mainly nodulus/uvula) to accurately estimate the direction of gravity due to abnormal otolithic (utricular) inputs. This can result in a directional error away from true earth vertical, and this bias is thought to cause erroneous head rotation signals that lead to pathological nystagmus https://collections.lib.utah.edu/ark:/87278/s6hj0x9w. (Video courtesy of Dr. Tzu-Pu Chang)