Hearing loss and cerebrospinal fluid pressure: case report and review of the literature.

Abstract

A decrease in cerebrospinal fluid pressure may result in an endolymphatic hydrops through a patent cochlear aqueduct or through the fundus of the internal auditory canal. This hydrops typically leads to low-frequency sensorineural hearing loss. We describe the case of a man who presented with a subjective and objective hearing loss in addition to a headache 4 days after he had undergone a dural puncture. We treated him with a standard epidural blood patch. Immediately after treatment, his hearing improved and his headache resolved.

Introduction

Several studies in the otolaryngology literature have examined the relationship between cerebrospinal fluid (CSF) pressure and sensorineural hearing. (1-7) It is presumed that the relationship involves the transmission of CSF pressure to and from the perilymphatic space through a patent cochlear aqueduct (figure 1). A loss of CSF pressure leads to a perilymphatic hypotonia or an endolymphatic hydrops. The features of this clinical scenario are analogous to those of Meniere's disease, in which patients with low CSF pressure often have a similar hearing loss, primarily in the low frequencies.

The mechanism of postdural puncture headache, which is occasionally associated with hearing impairment, is likewise based on low CSF pressure; in this case, the decrease is attributable to CSF leakage through the puncture site. (8) We tested the hypothesis that increasing CSF pressure in a patient with a hearing impairment associated with postdural puncture headache would eliminate both the hearing loss and the headache.

Case report

A 56-year-old man presented to our institution's pain clinic with a postdural puncture headache. Four days earlier, he had undergone a lumbar puncture during an evaluation of trigeminal neuralgia. The day after the puncture, a postural headache in the occiput developed. The pain radiated to his ears, neck, and proximal shoulders. The headache was positional and was completely relieved by his becoming supine.

At the pain clinic, the patient denied photophobia, fever, and chills. He reported that a hearing abnormality had developed concurrently with the headache. He said his hearing, particularly in the left ear, sounded as if he were "in a warehouse." He denied tinnitus, vertigo, otalgia, and otorrhea. He did not have a history of fluctuating hearing loss, and he had not previously experienced anything like this event. Findings on the physical examination were unremarkable, and no effusions or tympanic membrane retractions were noted. Standard audiometry, tympanometry, word recognition testing, and transient otoacoustic emission testing confirmed the hearing loss (figure 2, A).

The patient received a standard epidural blood patch, and his headache resolved immediately. Within 6 hours, he underwent follow-up audiometry performed by the same audiologist (J.K.S.) with the same equipment (figure 2, B). The second audiogram demonstrated a 10-dB improvement in pure tones at 250 and 500 Hz in the right ear. Word recognition in the left ear had increased from 50 to 90% at the 20-dB sensation level. Substantial changes in otoacoustic emissions were observed, with the right ear amplitude increasing from 7.7 to 12.1 dB and the left ear amplitude increasing from 7.1 to 9.2 dB. The patient reported no auditory difficulties and said that his hearing felt normal.

Discussion

Review of the literature. The relationship between CSF pressure and hearing has long been noted in the otolaryngology (1-7) and anesthesiology (9) literature. Cases of decreased hearing or tinnitus in spinal anesthesia patients were reported as early as 1956. (9)

Michel and Brusis described 9 patients who experienced hearing loss after undergoing myelography, lumbar puncture, and spinal anesthesia. (1) Hearing deficits were almost exclusively in the lower frequencies (125 to 1,000 Hz), a finding that is consistent with the findings in our case. Six of these 9 patients had a bilateral hearing loss. Six patients achieved a full recovery in less than 1 month without treatment, whereas the remaining 3 continued to experience various degrees of hearing loss.

Walsted et al tested 34 patients with pure-tone audiometry before and after spinal anesthesia (2) Most of these patients had a small but notable threshold shift at 500 Hz. The authors also described a patient with a low-frequency hearing loss after spinal anesthesia that resolved immediately with a blood patch. In a follow-up study, Walsted et al demonstrated that patients who underwent acoustic neuroma surgery experienced a decrease in pure-tone and speech reception thresholds in the contralateral ear. (3) In yet another study, Walsted et al compared control patients whose dura mater remained intact during neurosurgery with patients whose dura mater was opened and found that the latter group had significantly worse pure-tone and speech reception thresholds in the contralateral ear. (4) Finally, Walsted categorized 126 neurosurgical patients into three groups according to the amount of CSF they had lost intraoperatively and found that the level of hearing loss, the number of affected patients, and the number of frequencies involved in the contralateral ear were positively correlated with the amount of CSF lost. (5)

Hussain et al prospectively studied 35 women who were undergoing spinal anesthesia during cesarean section.(6) A comparison of pre- and postoperative pure-tone audiometry showed that 5 of these women developed a low-frequency hearing loss on the first postoperative day. By postoperative day 5, all 5 patients had experienced a full recovery without treatment.

In an experiment by Walsted et al, the authors drained CSF from 18 guinea pigs and compared their pre- and post-drainage electrocochleography results with those of 18 untreated control animals. (7) They noted a slightly higher compound action potential threshold and latency in the CSF-drained group.

[FIGURE 1 OMITTED]

Postdural puncture headache and the epidural blood patch. Excessive CSF loss through a dural puncture results in decreased intracranial pressure, which causes stretching of sensitive suspending structures, including the venous sinuses and their tributaries, the dural and cerebral arteries, and the dura mater itself. This results in the classic positional headache that is provoked by standing and relieved by reclining. Normally, the subarachnoid space replenishes its level of CSF within a few hours after fluid loss, and the headache resolves. However, if the communication through the subarachnoid space past the dura mater persists, a prolonged CSF leak and extended headache may occur. (9)

The usual treatment for a persistent CSF leak is an epidural blood patch. The anesthesiologist injects 5 to 15 ml of autologous blood into the epidural space over the site of the dural puncture, thereby patching the hole with the patient's own clotting factors. The introduction of this blood also exerts external pressure on the CSF column, thus normalizing the CSF pressure and immediately relieving the headache. (9)

Proposed pathogenesis of hearing loss. The cochlear aqueduct, which connects the perilymphatic space to the CSF-filled subarachnoid space, influences the relationship between low CSF pressure and hearing impairment. Patency is poor in the adult cochlear aqueduct, and it decreases throughout life. (10) In an effort to correlate changes in CSF pressure with perilymph pressure, Carlborg et al performed experiments in cats with open and artificially disrupted cochlear aqueducts. (11) They noted that CSF pressure and perilymphatic pressure equalized almost immediately when the aqueduct was open. When the aqueduct was closed, the shift toward equalization occurred more slowly and was usually incomplete. Carlborg et al hypothesized that equalization occurred as CSF flowed through small tributaries and possibly the fundus of the internal auditory canal when the cochlear aqueduct was disrupted. (11)

[FIGURE 2 OMITTED]

Presuming that the aqueduct is functionally patent, CSF pressure changes should be transmitted to the perilymphatic space. Furthermore, the results reported by Carlborg et al suggest that an obstructed aqueduct does not prevent equalization from occurring. (11) If the aqueduct is patent, loss of perilymph via decreased CSF pressure may lead to an endolymphatic hydrops. This condition resolves with either (1) the release of en dolymph through the endolymphatic sac, (2) the reaccumulation of perilymph through the aqueduct, or (3) perhaps another mechanism. Endolymphatic hydrops is a pathologic correlate of Meniere's disease. Its early course shares a common characteristic with hearing loss after a clinically significant CSF leak caused by dural puncture--to wit, both disorders are associated with a predominantly low-frequency hearing loss, as was seen in our patient.

It is interesting that our patient's symptoms were predominantly unilateral. The pure tones and otoacoustic emissions appeared to be more affected in the right ear, whereas the left ear showed a significant change in word recognition. We cannot explain this difference, but hearing loss associated with low CSF pressure often seems to affect one ear more than the other) (1,6,9) We hypothesize that the asymmetry of the hearing loss in our patient was the result of the unilaterally diminished patency of the cochlear aqueduct. Restricted aqueduct flow may prevent the equilibration of CSF, despite the presence of a CSF leak, and hearing loss may be unilateral. Our patient likely had unilateral stenosis of his cochlear aqueduct.

In conclusion, the relationship between decreased CSF pressure and hearing impairment is well documented. This report details an immediate improvement in subjective and objective hearing after the administration of an epidural blood patch to a patient with a hearing loss that had developed following a lumbar puncture.

References

(1.) Michel O, Brusis T. Hearing loss as a sequel of lumbar puncture. Ann Otol Rhinol Laryngol 1992;101(5):390-4.

(2.) Walsted A, Salomon G, Olsen KS. Low-frequency hearing loss after spinal anesthesia. Perilymphatic hypotonia? Scand Audiol 1991; 20(4):211-15.

(3.) Walsted A, Salomon G, Thomsen J, Tos M. Cerebrospinal fluid loss and threshold changes. 1. Hearing loss in the contralateral ear after operation for acoustic neuroma: An analysis of the incidence, time course, frequency range, size and pathophysiological considerations. Audiol Neurootol 1996;1(5):247-55.

(4.) Walsted A, Nielsen OA, Borum E Hearing loss after neurosurgery. The influence of low cerebrospinal fluid pressure. J Laryngol Otol 1994;108(8):637-41.

(5.) Walsted A. Effects of cerebrospinal fluid loss on hearing. Acta Otolaryngol Suppl 2000;543:95-8.

(6.) Hussain SS, Heard CM, Bembridge JL. Hearing loss following spinal anaesthesia with bupivacaine. Clin Otolaryngol Allied Sci 1996;21(5):449-54.

(7.) Walsted A, Nilsson P, Gerlif J. Cerebrospinal fluid loss and threshold changes. 2. Electrocochleographic changes of the compound action potential after CSF aspiration: An experimental study. Audiol Neurootol 1996;1(5):256-64.

(8.) Turnbull DK, Shepherd DB. Post-dural puncture headache: Pathogenesis, prevention and treatment. Br J Anaesth 2003;91(5): 718-29.

(9.) Vandam LD, Dripps RD. Long-term follow-up of patients who received 10,098 spinal anesthetics: Syndrome of decreased intracranial pressure (headache and ocular and auditory difficulties). J Am Med Assoc 1956;161(7):586-91.

(10.) Wlodyka J. Studies on cochlear aqueduct patency. Ann Otol Rhinol Laryngol 1978;87(1 Pt 1):22-8.

(11.) Carlborg BI, Konradsson KS, Carlborg AH, et al. Pressure transfer between the perilymph and the cerehrospinal fluid compartments in cats. Am J Otol 1992;13(1):41-8.

Matthew S. Pogodzinski, MD; Jon K. Shallop, PhD; Juraj Sprung, MD, PhD; Toby N. Weingarten, MD, Gilbert Y. Wong, MD; Thomas J. McDonald, MD

From the Department of Otorhinolaryngology (Dr. Pogodzinski, Dr. Shallop, and Dr. McDonald) and the Department of Anesthesiology (Dr. Sprung, Dr. Weingarten, and Dr. Wong), The Mayo Clinic, Rochester, Minn.

Corresponding author: Juraj Sprung, MD, Department of Anesthesiology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905. E-mail: [e-mail]