[Noninvasive assessment of intracochlear pressure. III. Case reports of patients with intracochlear hyper- and hypotension]

Profound hearing loss following surgery in pediatric patients with posterior fossa low-grade glioma

Background

Hearing loss may occur in patients with posterior fossa low-grade glioma who undergo surgery.

Methods

We retrospectively reviewed 217 patients with posterior fossa low-grade glioma, including 115 for whom results of hearing tests performed after surgery and before chemotherapy or radiation therapy were available. We explored the association of UHL with age at diagnosis, sex, race, tumor location, extent of resection, posterior fossa syndrome, ventriculoperitoneal shunt placement, and histology.

Results

Of the 115 patients, 15 (13.0%: 11 male, 6 black, 8 white, 1 multiracial; median age 7 years [range, 1.3-17.2 years]) had profound UHL after surgery alone or before receiving ototoxic therapy. Median age at tumor diagnosis was 6.8 years (range, 0.7-14.1 years), and median age at surgery was 6.8 years (range, 0.7-14.1 years). Patients with UHL had pathology characteristic of pilocytic astrocytoma (n = 10), ganglioglioma (n = 4), or low-grade astrocytoma (n = 1). Of these 15 patients, 4 underwent biopsy, 1 underwent gross total resection, 1 underwent near-total resection, and 9 underwent subtotal resection. UHL was more frequent in black patients than in white patients (OR 7.3, P = .007) and less frequent in patients who underwent gross total resection or near-total resection than in those who underwent subtotal resection (OR 0.11, P = .02).

Conclusions

Children undergoing surgery for posterior fossa low-grade glioma are at risk for UHL, which may be related to race or extent of resection. These patients should receive postoperative audiologic testing, as earlier intervention may improve outcomes.

Early neuro-otologic effects of three-dimensional irradiation in children with primary brain tumors

PURPOSE

Central nervous system (CNS) irradiation can cause sensorineural hearing loss. The relationship between the dose to the cochlea and the development of hearing loss is unknown. Conformal radiation therapy (CRT) techniques facilitate accurate cochlear dosimetry. We modeled hearing threshold levels (HTL) after CRT in children with localized primary brain tumors (ependymoma, low- or high-grade astrocytoma, craniopharyngioma, or CNS germinoma) by using cochlear dose and clinical variables.

PATIENTS AND METHODS

We evaluated 72 children (median age, 9.5 years) with audiograms before and every 6 months after CRT (median follow-up, 16.6 months; range, 4.3-42.6 months). We used a mixed-effects model to predict change in hearing for each ear as a function of time, cochlear dose, and clinical variables.

RESULTS

Hearing was affected the greatest in patients with CSF shunts and pre-CRT ototoxic chemotherapy, enhanced by cochlear dose, and was more prominent on the right side. Hearing impairment after CRT alone occurred at low and intermediate frequencies in patients with shunts and supratentorial tumors when the cochlear dose exceeded 32 Gy. Patients with shunts and central supratentorial tumors developed intermediate-frequency hearing loss after CRT alone regardless of dose.

CONCLUSIONS

Hearing loss during the first 4 years after CRT alone is uncommon, although patients with shunts and supratentorial tumors appear to be at increased risk for low- and intermediate-frequency effects. CSF shunting and increased cochlear dose enhance the effect of ototoxic chemotherapy. If possible, the average cochlear dose should be <32 Gy over a 6-week course of treatment until more specific dose data become available.

Hearing loss after spinal and general anesthesia: A comparative study

Hearing loss has been described after spinal anesthesia. We examined the hearing in patients before and after spinal and general anesthesia by pure tone audiometry (LdB: 125-1500 Hz; HdB: 2000-8000 Hz). Tympanic membrane displacement analysis was used to noninvasively monitor the intralabyrinthine and intracranial pressure. Eighteen patients received spinal anesthesia (G(SA)); 19 patients general anesthesia (G(GA)). Pure tone audiometry and TMD data were obtained preoperatively ((0)) and postoperatively on day 1 ((1)) and 2 ((2)). The mean threshold differences (Delta) in LdB(10) and LdB(20) were significantly different in G(SA) compared with G(GA) (DeltaLdB(10) + 0.15+/-3.07 dB vs. -1.34+/-3.77 dB, P = 0.05; DeltaLdB(20) -0.54+/-2.24 dB vs. -2.45+/-3.39 dB, P<0.01). However, there were no differences in DeltaHdB(10) between G(SA) and G(GA), but in DeltaHdB(20) (-1.40+/-3.95 dB vs -5.12+/- 6.35 dB, P = <0.01). We found a significant correlation between the magnitude of intraoperative intravascular volume replacement and low-frequency hearing loss. Tympanic membrane displacement values were not different pre- and postoperatively. Hearing was impaired after spinal and general anesthesia. Low-frequency hearing loss was correlated with intraoperative volume replacement. Tympanic membrane recordings did not reveal significant changes.

Limitations of the MMS-10 tympanic displacement analyser

Using the MMS-10 tympanic displacement analyser, the test-retest variation was determined in 20 normal hearing ears (ten subjects) for the measurement parameters Vi and Vm. Variations were found to be on average 60 nl for Vi and 72 nl for Vm. The consequences of these substantial test-retest variabilities for the applicability of the device and interpretation of the measurement results are discussed.