The presence of endolymphatic hydrops has been studied in many neurological disorders. The pathophysiological mechanisms may involve CSF pressure variations, transmitted to the innear ear. This hydrops could play a role in vestibular or cochlear symptoms. For the ENT specialist, the etiological diagnosis of endolymphatic hydrops is a challenge, and neurological etiologies must be known. The treatment of these neurological causes could be effective on cochleo-vestibular symptoms. The knowledge of endolymphatic hydrops could also be a target for noninvasive tests, able to estimate CSF pressure variations. For the neurologist, this could represent a useful tool for the diagnosis and follow-up, in some of these neurological disorders, related to a CSF pressure imbalance. The purpose of this paper is to summarize literature data on endolymphatic hydrops in neurological disorders. We define some neurological conditions, for which there is a particular interest in noninvasive investigations of endolymphatic hydrops.

Background The diagnosis of spontaneous or post‐traumatic intracranial hypotension mainly rely on clinical features and neuroimaging. In atypical presentations, other non‐invasive tests are missing to support the diagnosis of intracranial hypotension. The assessment of otoacoustic emissions (OAE) shown interest to monitor intracranial pressure mainly in cases of intracranial hypertension. This non‐invasive method was also assessed in response to pressure change after lumbar puncture. A few reports showed abnormal results of distortion product otoacoustic emissions (DPOAE) in cases of spontaneous or post‐traumatic intracranial hypotension. We describe additional results in a series of intracranial hypotension cases. We discuss the interest of DPOAE assessment in atypical presentations of intracranial hypotension. We review the other non‐invasive tests reported in literature. Methods We studied 4 atypical or recurrent cases of spontaneous or post‐traumatic intracranial hypotension by recording OAE in sitting then supine position. Results Unilateral or bilateral abnormal changes of DPOAE were recorded in all cases, in response to postural test. These changes were present even in the absence of vestibular symptoms. Conclusion The study of OAE may be a non‐invasive tool for the diagnosis of spontaneous intracranial hypotension.

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