Inner ear conductive hearing loss and downbeat nystagmus: A clinical case report

Abstract

A 49-year-old male, with 6-month history of sudden-onset hearing loss and oscillopsia that started 2 weeks after an outpatient surgery, is described in this report. Patient had a conductive hearing loss and down beat nystagmus. The imaging studies were within normal. Computer scan results suggested dehiscence due to thinning around the geniculate on the left side which brought the possibility of dehiscense of cochlea. However, an intrathecal MRI with gadolinium revealed a more prominent lateral filling of the left Cochlear Aqueduct (CA) was observed. A direct communication between cerebrospinal fluid (CSF) and inner ear is considered the reason for his mix hearing loss and nystagmus. The issue in this patient seems to be caused by alternation of CSF and perilymph barrier, not the third window issue of cochlea or superior canal. Through CA and possible through Schuknecht's canaliculus of internal auditory canal, the CSF started to infiltrate into the inner ear. This altered the both cochlear and labyrinthine functions and caused his air bone gap, down beat nystagmus and episodic vertigo. As risk factors for increased intracranial pressure such as obesity and CSF leaks are more commonly seen in SSCD patients, some these of SSCD may be suffering from this mechanism explained above. In the past, similar patients were reported as “occult” inner ear dehiscence, Ménière's or as perilymphatic fistula. We believe that these conditions must be differentiated in these patients as they seem to have a different pathophysiologic mechanism.