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|LETTER TO EDITOR
|Year : 2022 | Volume
| Issue : 4 | Page : 1685-1686
Central Apogeotropic Nystagmus Mimicking A Horizontal Canal “Cupulolithiasis” BPPV
Boby Varkey Maramattom1, P Sreeram2
1 Department of Neurology, Division of Neurotology, Aster Medcity, Kochi, Kerala, India
2 Department of Otorhinolaryngology, Division of Neurotology, Aster Medcity, Kochi, Kerala, India
|Date of Submission||24-Feb-2021|
|Date of Decision||31-Mar-2021|
|Date of Acceptance||05-May-2021|
|Date of Web Publication||30-Aug-2022|
Boby Varkey Maramattom
Departments of Neurology, Aster Medcity, Kochi, Kerala
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Maramattom BV, Sreeram P. Central Apogeotropic Nystagmus Mimicking A Horizontal Canal “Cupulolithiasis” BPPV. Neurol India 2022;70:1685-6
Horizontal central positional nystagmus [h-CPN] is uncommon. A 57-year-old man presented with intermittent vertigo and vomiting for 2 days duration. Examination revealed only saccadic pursuit eye movements with a normal Dix-Hallpike test. The McClure Pagnini test elicited a prolonged apogeotropic horizontal nystagmus (AgN) after a brief latency (higher intensity on the right side and lower intensity on the left side) suggestive of a left horizontal canal BPPV (Hc-BPPV) due to cupulolithiasis [Videos 1 and 2]. There were no other cerebellar signs. After repeated Gufoni manoeuvers (forced canalith repositioning manoeuvers × 5) did not ameliorate his vertigo, an MRI brain showed a left cerebellar infarction extending to the nodulus [Figure 1]. MRA showed a left vertebral artery V4 segment occlusion. He was started on antiplatelets, improved in 5 days, and was discharged.
|Figure 1: Diffusion-weighted MRI images showing a large left cerebellar PICA territory infarction. The blue arrow shows the infarct extending to the nodulus|
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Peripheral Hc-BPPV is of two types. Canalolithiasis produces geotropic nystagmus (GN) on both sides, which is worse toward the affected ear. Contrarily, cupulolithiasis produces apogeotropic nystagmus (AgN) on both sides, that is, less intense on the affected ear. CPN mimicking Hc-BPPV occurs in central vestibular disorders, with impaired central processing of peripheral vestibular signals [Figure 2].
|Figure 2: Cartoon [top row]—demonstrating the concordance between the actual and estimated gravitational signals processed by the vestibulocerebellum. Cartoon [bottom row]—demonstrating the discordance between the actual and estimated gravitational signals processed by the vestibulocerebellum. This leads to a “bias” and altered rotational feedback toward the naso-occipital line hat produces apogeotropic nystagmus on either side and may also produce a supine or sitting ipsilesional spontaneous horizontal nystagmus|
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A vestibulo-cerebellar pathway (central graviceptive pathway) relays rotational graviceptive information to a feedback center via a velocity storage mechanism (VSM). The VSM is activated by visual and vestibular cues and modified by gravity. It memorizes or stores rotational information. In the normal supine individual, in the ear down position, the estimated gravity feedback correctly points toward the bottom ear (actual and estimated gravity match). In lesions of this pathway, the estimated gravity is wrongly directed (biased) toward or away from the naso-occipital plane resulting in an actual versus estimated gravity mismatch. This is compensated by a corrective rotational cue resulting in sustained horizontal AgN or GN, mimicking the impulses that arrive in the vestibulocerebellum in Hc-BPPV.
In conclusion, our patient had AgN suggesting a left HC BPPV, which was in fact due to a left large cerebellar infarct involving the nodulus. He had very subtle central signs and the cerebellar infarct could have been missed without imaging. AgN should definitely alert the clinician to the possibility of a CPN. Central lesions should also be considered in the differential diagnosis of pure AgN or GN especially when the nystagmus is persistent (i.e., lasts >1 min), lacks fatigability, or is unresponsive to repeated canalith repositioning manoeuvers.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial Support and Sponsorship
Conflicts of Interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]