Spontaneous Intracranial Hypotension: A Rare Cause of Labyrinthine Hydrops

Abstract

Spontaneous intracranial hypotension should be considered as a possible cause of cochlear hydrops. We report a case of unilateral hearing loss attributed to spontaneous intracranial hypotension on the basis of characteristic abnormalities seen on magnetic resonance imaging. The diagnostic gold standards for intracranial hypotension are lumbar measurement of cerebrospinal fluid pressure and magnetic resonance imaging. The usual treatment is an autologous blood injection into the peridural spaces. The mechanism of hearing loss is thought to involve secondary perilymph depression due to a patent cochlear aqueduct. This perilymph depression would induce a compensatory expansion of the endolymphatic compartment, with a subsequent decrease in basilar or Reissner's membrane compliance. Endolymphatic hydrops can occur in the course of intracranial hypotension, and not only because of abnormal endolymph production or resorption. Hydrops can thus be classified into 1) syndromes of endolymphatic origin and 2) syndromes of perilymphatic origin, in which loss of perilymph induces compensatory expansion of the endolymphatic space.

Audiovestibular impairments associated with intracranial hypotension

“…Our patients mostly had unilateral low-frequency SNHL while one showed bilateral low-and high-frequencies SNHL. These are consistent with the findings of earlier case reports on intracranial hypotension, which described unilateral or bilateral low-frequency SNHL with occasional progression to downsloping mild-to-profound SNHL [6][7][8][9][10][11][12][13][14][15][16][17]. In contrast, the caloric tests were normal in all.…”

“…A study of 30 consecutive patients with intracranial hypotension has described neurotological symptoms including dizziness (30%), tinnitus (20%), aural fullness (20%), and hearing loss (3%) [1], while another reported auditory symptoms in approximately 70% of the patients [6]. Earlier reports have also documented unilateral or bilateral low-frequency sensorineural hearing loss on audiometry with or without vertigo, likewise in Meniere's disease (MD) [6][7][8][9][10][11][12][13][14][15][16][17]. However, previous studies have mostly focused on auditory dysfunction, and no study has attempted objective documentation of vestibular dysfunction in intracranial hypotension.…”

Spontaneous low cerebrospinal pressure/volume headaches

“…Frontotemporal dementia has been attributed to pressure on frontotemporal lobes and stupor and coma have been related to pressure on diencephalic structures. Upper limb radicular symptoms are likely caused by stretching of the nerve roots or pressure from dilated epidural venous plexus [41] or structural abnormalities of nerve root sleeves.…”

Spontaneous intracranial hypotension

“…The orthostatic nature of the headache is due to worsening of CSF hypotension that occurs secondary to gravitational pull when upright, as well as to increased sag/traction at the level of the cerebrum. Hypacusis and tinnitus are secondary to alterations in pressures of the perilymphatic system of the inner ear [20]. Symptoms localizing to the cranial nerves and brainstem are due to traction or compression of these structures.…”