The Geotropic Variant of Horizontal Canal BPPV

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: This is a patient with the geotropic (nystagmus beating towards the ground) variant of left horizontal canal (HC) benign paroxysmal positional vertigo (BPPV). In a patient with geotropic (nystagmus beating towards the ground) HC BPPV, by rapidly moving from a sitting to a supine position with the head straight, particles will move away from the ampulla to the most dependent portion of the canal, resulting in an ampullofugal flow and nystagmus that beats away from the affected side. If otoconia are located close to the ampulla as they typically are with apogeotropic HC BPPV, particles will move towards the cupula and provoke an ampullopetal flow and nystagmus that beats towards the affected side. The right-beating nystagmus (RBN) when going from upright to supine position in this patient with geotropic HC BPPV suggested that the left HC was involved. ; With supine roll testing (where the head is rolled 90 degrees to the right and to the left), there was weaker right-beating nystagmus (RBN) with right roll test, and stronger LBN with left roll test - this also suggests that the left HC was involved. Since the otoconia are typically located in the most dependent part of the canal in geotropic HC BPPV, when the left side is affected, rotating the head 90 degrees to the left allows particles to move towards the ampulla, producing an ampullopetal flow which is an excitatory stimulus - i.e., a robust LBN will result. Rotating the head 90 degrees to the right allows particles move away from the cupula (ampullofugal), which is an inhibitory stimulus - i.e., a weaker RBN will result. ; In contrast, supine roll testing in apogeotropic HC BPPV results in nystagmus that is stronger towards the unaffected side (e.g., stronger LBN with right roll compared to RBN with left roll suggests left HC involvement). The opposite is true of the geotropic variant, where nystagmus is stronger with the affected ear down (e.g., left ear was the affected side, and left roll test demonstrated stronger nystagmus as compared to right roll test). Or more simply, when dealing with geo- or apogeo- HC BPPV, the nystagmus is more intense when beating toward the affected ear. ; [[Number of Videos and legend for each: A patient with the geotropic variant of horizontal canal BPPV]] 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: This is a patient with the geotropic (nystagmus beating toward the ground) variant of left horizontal canal (HC) benign paroxysmal positional vertigo (BPPV). In a patient with geotropic (nystagmus beating toward the ground) HC BPPV, by rapidly moving from a sitting to a supine position with the head straight, particles will move away from the ampulla to the most dependent portion of the canal, resulting in an ampullofugal flow and nystagmus that beats away from the affected side. If otoconia are located close to the ampulla as they typically are with apogeotropic HC BPPV, particles will move toward the cupula and provoke an ampullopetal flow and nystagmus that beats toward the affected side. The right-beating nystagmus (RBN) when going from upright to supine position in this patient with geotropic HC BPPV suggested that the left HC was involved. With supine roll testing (where the head is rolled 90 degrees to the right and to the left), there was weaker right-beating nystagmus (RBN) with right roll test, and stronger LBN with left roll test-this also suggests that the left HC was involved. Since the otoconia are typically located in the most dependent part of the canal in geotropic HC BPPV, when the left side is affected, rotating the head 90 degrees to the left allows particles to move toward the ampulla, producing an ampullopetal flow which is an excitatory stimulus-i.e., a robust LBN will result. Rotating the head 90 degrees to the right allows particles move away from the cupula (ampullofugal), which is an inhibitory stimulus-i.e., a weaker RBN will result. In contrast, supine roll testing in apogeotropic HC BPPV results in nystagmus that is stronger toward the unaffected side (e.g., stronger LBN with right roll compared to RBN with left roll suggests left HC involvement). The opposite is true of the geotropic variant, where nystagmus is stronger with the affected ear down (e.g., left ear was the affected side, and left roll test demonstrated stronger nystagmus as compared to right roll test). Or more simply, when dealing with geo- or apogeo-HC BPPV, the nystagmus is more intense when beating toward the affected ear https://collections.lib.utah.edu/details?id=1281862. (Video courtesy of Dr. Marco Mandala)