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Barany Society includes bilateral typical posterior semicircular canal benign paroxysmal positional vertigo (PSC-BPPV) in its classification of multicanal subtype. In the past decade, less-common and atypical subtypes of PSC-BPPV, like short-arm and non-ampullary arm posterior semicircular canalolithiasis, have emerged, requiring the conduct of conventional and auxiliary positional tests on both sides to uncover their bilaterality. Authors hereby report three atypical less-common subtypes of bilateral PSC-BPPV, discussing their clinicodemographic profiles, management by repositioning maneuvers and physical therapy, and follow up. Both Case 2 and Case 3 are precisely tri-canalolithiasis (bilateral ampullary arm posterior semicircular canalolithiasis with co-occurring right non-ampullary arm posterior semicircular canalolithiasis in Case 2 and bilateral short arm with co-occurring left ampullary arm posterior semicircular canalolithiasis in Case 3), which has not been reported previously in the literature. There has been only one previously reported case of bilateral non-ampullary arm semicircular canalolithiasis, and it is now observed in Case 1.

Vestibular rehabilitation therapy (VRT) mainly comprises physical therapies that encourage head, eye, and truncal movements, accelerating the recovery of patients with acute peripheral labyrinthine dysfunction. VRT aims to improve vestibular hypofunction by reinforcing vestibulo-ocular, vestibulospinal, and vestibulocollic reflexes. An asymmetry in peripheral vestibular inputs from the pair of membranous labyrinths to the central nervous system frequently results from vestibular lithiasis, causing benign paroxysmal positional vertigo (BPPV). The article discusses the pathophysiology, subtypes, and diagnostic oculomotor patterns generated during positional tests in each subtype of BPPV. Accurate identification of the pathophysiology (canalolithiasis versus cupulolithiasis) as well as the involved semicircular canal (localization and lateralization) is crucial for the unerring VRT of BPPV by physical therapies and/or repositioning maneuvers. The article elaborates the currently known variants of BPPV, the anatomico-physiological correlation between otoconial location and oculomotor patterns generated during the diagnostic positional tests in terms of the direction, latency, and duration of the elicited positional nystagmus [Figure 1] and [Figure 2]; [Table 2]. A detailed description of the treatment of different BPPV subtypes with repositioning maneuvers and/or physical therapy is given [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]; [Table 3].

A graviceptive heavy posterior cupula typically results from cupulolithiasis and clinically manifests as short vertigo spells when the head moves in the provocative position. Half-Hallpike test (HHT) in posterior cupulolithiasis (PSC-BPPV-cu) elicits an upbeating ipsitorsional nystagmus (UBITN), which lasts more than a minute as per the consensus criteria developed by the Barany Society. In the last decade, cases with canalolithiasis in the short arm of the posterior semicircular canal (PSC-BPPV-sa), wherein the otoconial debris falls on the utricular side of the posterior cupula on getting up from supine, rendering it heavy (graviceptive), have been reported. Such patients complain of sitting-up vertigo, associated with a constant disequilibrium, and anteroposterior truncal oscillations are recorded by ad hoc posturography in many of these patients. The oculomotor patterns generated in such patients during the HHT may be identical to those resulting from PSC-BPPV-cu. Rarely do the two conditions (PSC-BPPV-cu and PSC-BPPV-sa) coexist. Nine cases of graviceptive heavy cupula were diagnosed at our center over a period of 6 months from September 1, 2022, to March 31, 2023, with their characteristic diagnostic oculomotor patterns, distinguishing features, and management discussed. We propose a grading system for the inversion test during the HHT that reliably distinguishes PSC-BPPV-cu from PSC-BPPV-sa, as well as when the two conditions coexist.

Apogeotropic variant of posterior semicircular canal benign paroxysmal positional vertigo (apo-PSC-BPPV) is a rare peripheral vestibular disorder, characterized by paroxysms of positionally triggered dizzy spells associated with non-positional disequilibrium. It is diagnosed by observing characteristic diagnostic oculomotor responses (torsional downbeating positional nystagmus) during positional testing (Dix-Hallpike and enhanced straight head hanging tests), in conjunction with a response to physical therapy. Much rarer anterior semicircular canal benign paroxysmal positional vertigo (ASC-BPPV) elicits identical oculomotor responses during positional testing. Propter hoc, response to physical therapy at short-term follow-up is crucial in distinguishing the apo-PSC-BPPV from ASC-BPPV. We are presenting a case series of seven patients of apo-PSC-BPPV (of which three were bilaterally affected), who attended our otoneurology center, between February 1, 2023, and July 31, 2023. Demographic profile, clinical course, and physical therapy with responses at short-term follow-up at 1 hour and after 24 hours are discussed.

Monohalomethanes are alkylating agents that have been used as methylating agents, laboratory reagents, refrigerants, aerosol propellants, pesticides, fumigants, fire-extinguishing agents, anesthetics, degreasers, blowing agents for plastic foams, and chemical intermediates. Compounds in this group are methyl chloride, methyl bromide, methyl iodide (MI), and methyl fluoride. MI is a colorless volatile liquid used as a methylating agent to manufacture a few pharmaceuticals and is also used as a fumigative insecticide. It is a rare intoxicant. Neurotoxicity is known with both acute and chronic exposure to MI. We present the characteristic magnetic resonance imaging (MRI) brain findings in a patient who developed neuropsychiatric symptoms weeks after occupational exposure to excessive doses of MI.