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A 53-year-old man presents to a hospital emergency department (ER) in Copenhagen, Denmark after suffering sudden complete loss of hearing in both ears. He is accompanied by a friend, who tells clinicians that the hearing loss developed while the patient was watching television, and he also mentions an unusual speech problem, although he didn't elaborate. The hearing did gradually come back, however, over the next 4 hours.

The patient is assessed in the ED by an internal medicine resident, who learns that the patient is a smoker, and that his medical history also includes high blood pressure, hypercholesterolemia, and chronic heart failure. He also previously had an ischemic stroke which resulted in reduced sensation in his extremities on his left side and a mild motor speech disorder.

None of these abnormalities, however, are observed at the time of the ED examination, and the patient is discharged the same day, with a referral to the hospital neurology department.

The patient presents to the hospital neurology department 2 days later, and undergoes a neurological examination, which identifies slight loss of hearing on the left side, as well as reduced sensation for touch and pain on the left side. No other abnormal neurological findings are detected.

Clinicians consult an ear, nose, and throat specialist, who determines that it is not necessary to see the patient. Blood tests are negative for signs of infection, and assessments of kidney, liver, and lipid status, and glucose and thyroid stimulating hormone are unremarkable except for a leucocyte count of 9.8 × 10⁹ mg/L.

The patient is not febrile and has no other signs of infection.

Magnetic resonance imaging (MRI) reveals a subacute temporoparietal infarct on the left side involving the insular cortex, and there is also evidence of an older infarct in the right temporoparietal region.

Clinicians perform a routine stroke work-up, including ultrasound of the carotid arteries, electrocardiography, telemetry, blood cholesterol and HbA1c, and blood pressure.

MRI of the heart, however, reveals a large aneurysm and an old mural thrombus in the left ventricle.

The patient is instructed to return to the stroke outpatient clinic in 3 months for a follow-up assessment, at which time he has no complaints.

Discussion

The authors presenting this of a 53-year-old man with transient complete bilateral hearing loss note that when considering possible differential diagnoses in patients with sudden bilateral deafness, clinicians should always prioritize immediate stroke work-up since acute revascularizing treatment is highly time-dependent.

While sudden-onset bilateral cortical deafness is a very rare symptom of stroke, this patient's hearing loss was explained by an infarction shown on MRI, which revealed a subacute temporoparietal ischemic lesion in the left cerebral hemisphere involving the insular cortex and an older infarction in the right temporoparietal region.

The location of such lesions do not typically cause motor deficits, but rather tend to be associated with sensory and cognitive symptoms such as aphasia, which can be challenging to recognize in a suddenly deaf patient, the case authors note.

In adults, sudden sensorineural hearing loss is typically unilateral and idiopathic. Conversely, acute bilateral deafness is extremely rare and is generally related to systemic diseases such as toxicity, infection, autoimmune or neoplastic conditions, or vascular events.

A of 103 reported cases of bilateral sudden sensorineural hearing loss found that patients with the bilateral rather than unilateral loss had more profound hearing loss, with poorer recovery and a 35% mortality rate.

Vascular causes for the condition include vasospasms after subarachnoid hemorrhage, , and and most patients have unilateral damage in the primary auditory cortex, and subsequently develop a vascular lesion on the opposite side leading to deafness in both ears.

Normal function of both peripheral and central auditory pathways is required for hearing, with auditory stimuli from each ear ending in the left and right sides of the brain cortex.

As shown in this from the case report, some of the nerve fibers from the cochlea project to the ipsilateral superior olivary nucleus and some of the fibers decussate to the contralateral superior olivary complex. Thereafter, the majority of the fibers travel ipsilaterally to the inferior colliculus and the rest to the contralateral inferior colliculus. From the ipsilateral inferior colliculus, the nerve fibers project to the medial geniculate nucleus in the thalamus and finally to the primary auditory cortex.

Thus, the case authors explain, a single cortical lesion cannot result in one-sided hearing loss; bilateral cortical damage is necessary to cause bilateral cortical deafness.

The authors caution that because ischemic and hemorrhagic strokes only very rarely result in acute symmetrical lesions on both sides of the cortex, clinicians may not suspect a vascular etiology when a patient presents with acute onset of bilateral hearing loss. An appropriately targeted work-up can therefore aid in timely diagnosis.

A 2019 from the American Academy of Otolaryngology–Head and Neck Surgery advises against:

• Ordering routine computed tomography of the head in the initial evaluation of a patient with presumptive sudden sensorineural hearing loss

• Obtaining routine laboratory tests in patients with sudden sensorineural hearing loss

• Routinely prescribing antivirals, thrombolytics, vasodilators, or vasoactive substances for such patients

Conversely, the guideline makes several positive recommendations, including the following:

• Clinicians should assess patients with presumptive sudden sensorineural hearing loss through history and physical examination for bilateral sudden hearing loss, recurrent episodes of sudden hearing loss, and/or focal neurologic findings

• In patients with sudden hearing loss, clinicians should obtain, or refer to a clinician who can obtain, audiometry as soon as possible (within 14 days of symptom onset) to confirm the diagnosis of sudden sensorineural hearing loss

• Clinicians should evaluate patients with sudden sensorineural hearing loss for retrocochlear pathology by obtaining MRI or auditory brainstem response

Regarding the case of this patient, the authors note that he was initially examined in the ED but was discharged without further assessment since he had recovered his hearing. In retrospect, however, the best procedure for this patient would have been an acute referral for a complete stroke work-up, the team writes.

In addition, the patient's coexisting speech problem, which was not mentioned on the initial ED contact, was likely actually aphasia rather than speech impairment due to the hearing loss; aphasia can be challenging to fully diagnose in a completely deaf patient, the authors note.

Because temporoparietal lesions do not typically cause motor symptoms, they may be difficult to recognize for clinicians who are not specialists in stroke. And while sudden bilateral hearing loss may also be due to the type of conditions described above, such as toxic, infectious, autoimmune, paraneoplastic, or infectious pathogeneses, patients with these conditions are unlikely to have spontaneous rapid and complete recovery.

Moreover, these conditions would be associated with other symptoms, such as fever, headache, or weight loss, before hearing loss occurred.

Conclusion

The case authors conclude that even if a patient does not have apparent cerebrovascular risk factors, immediate stroke work-up should be considered in all patients with sudden onset of bilateral deafness, because it is possible to treat the patient with intravenous thrombolysis in case of stroke.

If the hearing loss resolves spontaneously within 24 hours, it is highly likely due to a transient ischemic attack, and eventually, if stroke is excluded, further work-up for other conditions can be carried out subsequently.

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