Abstract
Spontaneous intracranial hypotension (SIH) is a syndrome characterized by cerebrospinal fluid (CSF) hypovolaemia usually occurring secondary to a spontaneous tear in the dura (1). In the majority of patients with SIH, the cardinal clinical feature is orthostatic headache. However, during the past decade, a wide spectrum of associated neurological and/or neuro-otological symptoms have been described (1). This report describes a patient with recurrent CSF leaks presenting initially 5 years ago as an isolated thunderclap headache and then, more recently, as recurrent sudden-onset hearing loss.
Case report
Previous episode of spontaneous intracranial hypotension presenting as a thunderclap headache
Five years ago, this 51-year-old man developed an unprovoked, sudden-onset, explosive, holocranial headache with associated neck pain and right-sided tinnitus. The headache was relieved rapidly by assuming a supine position and was provoked quickly upon rising to an upright position. Ten days after headache onset, gadolinium-enhanced magnetic resonance imaging (MRI) of the brain demonstrated abnormal, uniform pachymeningeal enhancement. Gadolinium-enhanced MRI of the cervical cord demonstrated pachymeningeal enhancement with a prominent, enhancing, extra-axial fluid collection extending from the anterior foramen magnum to the upper thoracic spine. Ten weeks after symptom onset, he underwent a lumbar epidural blood patch with 18 cm3 of autologous blood. Immediate improvement was noted with mild postural headache and neck pain persisting for several weeks. Two weeks after the blood patch, a repeat MRI of the brain and cervical cord demonstrated significant but incomplete improvement. Six months after the blood patch, repeat gadolinium-enhanced MRI of the brain, cervical, and thoracic cord demonstrated no abnormalities. He has had no subsequent problems with headache.
Current episode of sudden-onset hearing loss
Six months ago, this 51-year-old man abruptly lost hearing in the right ear. While not deaf, the patient had substantially diminished hearing and he could not hear using the telephone with the affected ear. There were no accompanying headache, otological, neurological, or systemic symptoms. There was no history of straining, head trauma, barotrauma, exposure to ototoxic drugs, or otological surgery. His hearing spontaneously recovered over a few days, and he remained asymptomatic for approximately 10 days. He then went scuba diving while on vacation, and soon after he again lost hearing in the right ear. Once more, hearing loss spontaneously resolved over a few days. Subsequently, otolaryngology assessment demonstrated a normal, type A tympanogram and audiometry revealed a high-frequency sensorineural hearing loss. Erythrocyte sedimentation rate (ESR), thyroid-stimulating hormone, and T4 were normal, and treponemal antibody testing was non-reactive. Gadolinium-enhanced MRI of the brain demonstrated diffuse panchymengingeal enhancement, particularly in the posterior fossa and extending bilaterally into the internal auditory canals (see Figs 1 and 2). Gadolinium-enhanced MRI of the cervical and thoracic cord demonstrated a ventrally located extra-arachnoid fluid collection from C1 to C7 with engorgement of the epidural venous plexus. Although the patient was asymptomatic, follow-up MRI 3 months later was unchanged.
Axial T1-weighted gadolinium-enhanced brain MRI demonstrating pachymeningeal enhancement surrounding posterior fossa structures.
Coronal T1-weighted gadolinium enhanced brain MRI demonstrating diffuse thin continuous pachymeningeal enhancement over the cerebral convexities and tentorium cerebelli.
Discussion
Altered hearing (hypo- or hyperacusis) often accompanies headache in patients with SIH but only rarely has it been reported without concomitant headache (2–4). Nonetheless, there are several reports of isolated hearing loss as a manifestation of CSF hypovolaemia secondary to: lumbar puncture (5–10), myelography (11–13), inadvertent dural puncture during a cervical block (14), spinal anaesthesia (15–24), over-shunting (25–28), and following breach of the dura during neurosurgical procedures (29–31). Furthermore, in several of these cases, epidural blood patches resulted in rapid and complete return of normal hearing (32–36). In fact, isolated chronic progressive hearing loss attributable to chronic overshunting has been reported to improve following shunt revision (25).
The headache typically produced by SIH is thought to be secondary to traction or distortion of anchoring pain-sensitive structures as the brain descends secondary to CSF hypovolaemia (1). Dilation of cerebral veins and venous sinuses may also contribute to headache. Neurological impairment may be related to secondary subdural fluid collections and/or compression or distortion of posterior fossa structures or nerve roots (1). Otological symptoms (tinnitus, hypo- or hyperacusis, dysequilibrium) may result from traction on the eighth cranial nerve or compensatory venous dilation and fluctuations in endolymphatic pressure, which may lead to vestibulocochlear dysfunction.
Sudden sensorineural hearing loss (SHL) loss is uncommon (1 : 5000) and remains a controversial area in otolaryngology with no uniform approach to diagnosis or treatment (37, 38). In the vast majority of patients, hearing loss is unilateral and occurs within minutes to hours. The differential diagnosis of SHL is extensive and includes infection (viral cochleitis, bacterial meningitis, syphilis), medication-induced (i.e. ototoxic drugs such as gentamicin), vascular (i.e. embolic, thrombotic, or haemorrhagic), autoimmune-mediated, local compression (acoustic neuroma), noise-induced (i.e. acute acoustic trauma from gunfire or explosions), demyelination (i.e. multiple sclerosis), or perilymph fistula (39, 40). The work-up for SHL includes a clinical examination by otolaryngology, audiometry, computed tomography scan with temporal bone views, serology (for complete blood cell count, ESR, syphilis screen), and MRI (for ischaemic or locally compressive lesions). In most cases, the diagnosis is idiopathic SHL. Approximately one-third of patients have a return to normal hearing, one-third have moderate recovery, and one-third remain severely impaired. When an identifiable cause is uncovered, treatment is targetted; when the SHL is idiopathic, numerous non-specific therapies have been advocated, including corticosteroids, vasodilators, anticoagulation, vitamins, and bed rest (37, 38).
In this case, clinical history, otolaryngology evaluation, serologic testing, and MRI failed to identify an alternate aetiology other than SIH. MRI clearly identified a recurrent CSF leak. Recurrent idiopathic SHL is quite uncommon and while this patient could have had concurrent asymptomatic SIH and recurrent idiopathic SHL, we believe this is unlikely. Given the radiographic evidence of a recurrent CSF leak, the known propensity for SIH to cause otological disturbances, and following the wisdom of Occam's razor, it is justifiable to use the principle of parsimony to implicate SIH as the aetiology of this patient's recurrent hearing loss.
This case highlights several important clinical features of SIH; namely, that thunderclap headache can be the initial presenting symptom of SIH, that recurrent attacks of SIH can occur and that they may be separated by years, and that isolated sudden-onset hearing loss may be the only clinical manifestation of SIH. It is important for physicians to be aware of this unique aetiology of SHL, especially considering that the underlying cause of SHL often remains elusive despite a thorough investigation and that treatments are widely non-specific. There continues to be ongoing scholarly debate regarding the most appropriate and cost-effective neuroimaging strategy to evaluate SHL. While some authorities feel a high-resolution, non-enhanced, fast spin echo, T2-weighted MR sequence is sufficient, others believe that a gadolinium-enhanced MRI is necessary (39–42). This case provides further argument for the utility of gadolinium-enhanced MRI in patients with unexplained sudden-onset hearing loss. Whether due to iatrogenic causes or SIH, hearing loss due to CSF hypovolaemia may spontaneously improve as it did in this case, or the patient may require prolonged bed rest or an autologous epidural blood patch.