Auditory dysfunction is a common clinical symptom that can induce profound effects on the quality of life of those affected.
Conductive Hearing Loss
Mixed Hearing Loss
Hearing loss can be associated with a decrease in cerebrospinal fluid (CSF) pressure because changes in CSF pressure induce changes in perilymph pressure. Hearing loss after neurosurgical procedures have been reported.
Identification and protection of the cochlea during anterior petrosectomy is key to prevent hearing loss. Currently, there is no optimal method to infer the position of the cochlea in relation to the Kawase quadrangle, therefore damage to the cochlea during anterior petrosectomy remains a substantial risk.
Kawase approach was simulated in eleven specimens. After a subtemporal approach, foramen spinosum and foramen ovale were identified. Anterior petrosectomy was performed and the upper dural transitional fold (UDTF) was identified. Two virtual lines, from foramen spinosum (Line A), and the lateral rim of the foramen ovale (Line B), were projected to intersect the UDTF perpendicularly. The cochlea was exposed and the distances between Lines A and B and the closest point of the outer rim and membranous part of the cochlea were measured.
The average distance between Line A to the bony and membranous edges of the anteromedial cochlea was -0.62±1.38 mm and 0.38±1.63 mm, respectively. The average distance between Line B to the bony and membranous edges of the cochlea was 1.82±0.99 mm and 2.78±1.29 mm, respectively. Line B (cochlear safety line) never intersected the cochlea.
The cochlear safety line is a reliable landmark to avoid the cochlea during the Kawase approach. When expanding the anterior petrosectomy posteriorly, the “cochlear safety line” may be used as a reliable landmark to prevent exposure of the cochlea, therefore preventing hearing loss 1).
Clinical information on hearing loss after the placement of ventriculoperitoneal (VP) shunts, the most commonly used CSF shunt for hydrocephalus patients, is limited.
There is substantial evidence that cerebrospinal fluid circulation and pressure abnormalities can produce auditory dysfunction. Several indirect mechanisms may explain association between hydrocephalus and hearing loss, including mass effect, compromise of the auditory pathway, complications of prematurity, and genetically mediated hydrocephalus and hearing loss. Nevertheless, researchers have proposed a direct mechanism, which Satzer et al. term the hydrodynamic theory. In this hypothesis, the intimate relationship between CSF and inner ear fluids permits relative endolymphatic hydrops or perilymphatic hydrops in the setting of CSF pressure disturbances. CSF is continuous with perilymph, and CSF pressure changes are known to produce parallel perilymphatic pressure changes. In support of the hydrodynamic theory, some studies have found an independent association between hydrocephalus and hearing loss. Moreover, surgical shunting of CSF has been linked to both resolution and development of auditory dysfunction. The disease burden of hydrocephalus-associated hearing loss may be large, and because hydrocephalus and over-shunting are reversible, this relationship merits broader recognition. Hydrocephalic patients should be monitored for hearing loss, and hearing loss in a patient with shunted hydrocephalus should prompt further evaluation and possibly adjustment of shunt settings 2).
Hearing thresholds may increase following VP shunt placement, possibly due to secondary endolymphatic hydrops 3).