Endolymphatic Hydrops and Cerebrospinal Fluid Pressure: A 30-Year Update

Dixon and Jones ¹ reported hearing loss from high-pressure hydrocephalus. Clearly, if interpreted correctly, this case raises the important question of why so few with high cerebrospinal fluid (CSF) pressures are deaf. In fact, they could only find 1 previous case of hydrocephalus-associated sensorineural hearing loss. ² They ignored a previous review that concluded that it was low and not high CSF pressures that caused auditory problems. ³

Cerebrospinal fluid hypotension or lowered perilymph pressure from many causes can clearly cause increased pressure/volume of the endolymph (hydrops),^2-4 since if the perilymph compartment diminishes, the endolymph one will expand. There is now an onus on those proposing otological sequelae to CSF hypertension to document unimpeachable cases where low and high CSF pressure syndromes had been differentiated.^3,4

The single case cited ² is problematic. First, a 13-year-old boy coping in the classroom without auditory/vestibular complaints could not plausibly present with sudden bilateral 70- to 80-dB deafness. I would never trust a single pure-tone audiogram to give a valid measure of hearing loss, even if I had done it myself, especially in adolescents, in whom nonorganic hearing loss is common. Dixon and Jones ¹ recommended just this test, although in practice they had also done speech audiometry in their 14-year-old girl, confirming the accuracy of her audiogram. Second, the boy had disabling dizzy headaches that worsened during the day, characterizing CSF hypotension, not hypertension (worse in mornings).

The only case cited ² of CSF pressure reduction leading to resolution of hydrops was the study of shunted idiopathic aqueductal stenosis that prompted my review. ³ I proposed that low, not high, CSF pressures induced the hydrops in these and other cases I reviewed. Many had Chiari syndrome, a definite consequence of CSF loss or hypotension. ⁴ Low-pressure hydrocephalus can present as aqueduct stenosis, ⁴ and low and high CSF pressure syndromes are very similar. ³ Rekate ⁴ spent 25 years developing a sophisticated model of CSF dynamics before realizing that he had omitted the cortical subarachnoid space, a crucial component especially to otologists as the cochlear aqueduct opens there. Benign intracranial hypertension is often accompanied by hydrops, reversible by shunting. Sismanis ⁵ crucially concluded that perilymph hypertension was not the obvious cause of the hydrops because digital occlusion of the ipsilateral jugular vein reversed the hydrops. Neck wrapping with an elastic bandage increases pressure/volume in the cortical subarachnoid space, ⁴ thereby increasing perilymph pressure. This confirms hydrops is due to low, not high, perilymph pressure.