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The brainstem is the narrow stalk connecting the spinal cord to the cerebral hemispheres. It contains the vestibular nuclei, which process balance information from the inner ear; the cochlear nuclei, which relay auditory signals; the oculomotor nuclei, which control eye movements; and the reticular activating system, which governs consciousness. The entire brainstem depends on blood supplied by the vertebrobasilar circulation. When this circulation is interrupted by a stroke, the result can be severe vertigo, disequilibrium, hearing loss, or a combination of these symptoms.
Vertigo is commonly divided into peripheral vertigo, originating from the inner ear or the vestibular nerve, and central vertigo, originating from the brainstem or cerebellum. Most cases of acute vertigo are peripheral and benign, such as vestibular neuritis or benign paroxysmal positional vertigo. However, a brainstem stroke is a central cause of vertigo that must not be missed. Features suggesting a central origin include severe imbalance out of proportion to dizziness, vomiting, double vision, slurred speech, facial numbness, limb weakness, and hearing loss that appears suddenly in combination with other neurological signs.
Several well-defined brainstem stroke syndromes produce vertigo or hearing symptoms. Knowing the arterial territories helps clinicians predict which structures are affected and how rapidly the patient may deteriorate.
Lateral medullary syndrome, also called Wallenberg syndrome, is the most common brainstem stroke syndrome that presents with vertigo. It is usually caused by occlusion of the intracranial vertebral artery or the posterior inferior cerebellar artery (PICA), affecting the lateral medulla. Patients experience sudden severe vertigo, nausea, and nystagmus, along with ipsilateral Horner syndrome (drooping eyelid, small pupil, absent facial sweating), ipsilateral loss of pain and temperature sensation on the face, contralateral loss of pain and temperature sensation on the body, hoarseness, and difficulty swallowing. Because the cochlear nucleus is not typically within the infarcted territory, profound hearing loss is unusual in this syndrome, although it can occasionally occur.
The anterior inferior cerebellar artery (AICA) supplies the lateral pons, the middle cerebellar peduncle, and the inner ear via the labyrinthine artery. The labyrinthine artery is an end artery, meaning it has no collateral circulation. A stroke in the AICA territory therefore frequently produces combined vertigo and hearing loss on the affected side. This is a central vestibular syndrome with a peripheral auditory component. Along with acute vertigo and sudden ipsilateral hearing loss, patients may have tinnitus, facial weakness, facial numbness, Horner syndrome, limb ataxia, and loss of pain and temperature sensation over the contralateral body. AICA strokes are sometimes mistaken for severe vestibular neuritis with hearing loss, but the presence of additional brainstem signs usually clarifies the diagnosis.
The superior cerebellar artery (SCA) supplies the superior surface of the cerebellum, the upper cerebellar peduncles, and portions of the midbrain and pons. Vertigo occurs in a substantial proportion of SCA strokes, but hearing loss is uncommon because the cochlear pathways are not directly in the territory. Typical symptoms include sudden vertigo, headache, nausea, gait ataxia, dysarthria, and incoordination of the limbs. Because the infarct often involves the cerebellum more than the brainstem, it may mimic an inner ear disorder or a migraine variant. A high index of suspicion is needed when ataxia is severe.
The basilar artery is the main trunk formed by the union of the two vertebral arteries. Basilar artery occlusion is a catastrophic stroke subtype. It may begin with prodromal vertigo, tinnitus, and hearing loss lasting hours to days before sudden progression to bilateral weakness, cranial nerve palsies, pupillary abnormalities, and coma. In some patients, the initial presentation is isolated vertigo, which makes early recognition particularly difficult. Occlusion of the basilar artery can lead to the locked-in syndrome, in which the patient is aware but unable to move or speak due to destruction of the ventral pons. Survival depends on rapid recanalisation with intravenous thrombolysis or mechanical thrombectomy.
The HINTS examination is a widely used bedside test for acute vestibular syndrome. It evaluates three features: head impulse test, direction-changing nystagmus, and test of skew. A normal head impulse test, nystagmus that changes direction with gaze, or a vertical misalignment of the eyes (skew deviation) strongly suggests a brainstem stroke rather than a peripheral vestibular disorder. In addition, central nystagmus may be purely vertical or torsional, whereas peripheral nystagmus is typically horizontal and suppressed by visual fixation. Hearing loss in the setting of acute vertigo should always raise the possibility of AICA territory stroke, especially when accompanied by facial weakness or cerebellar ataxia.
Non-contrast computed tomography of the head is often normal in the first hours of a posterior circulation stroke because of beam-hardening artifact from the skull base. Magnetic resonance imaging with diffusion-weighted imaging is the preferred test for detecting acute brainstem infarcts, although even this may be falsely negative within the first few hours. In patients presenting with acute vertigo and hearing symptoms, repeated neurological assessment is essential because brainstem signs may evolve over time. When a brainstem stroke is confirmed, treatment depends on the time from symptom onset. Intravenous thrombolysis with alteplase or tenecteplase is given within the appropriate time window, and endovascular thrombectomy may be performed for basilar artery occlusion or proximal large-vessel occlusion. Patients with disabling vertigo often also benefit from vestibular rehabilitative therapy after the acute phase.
Vertigo and hearing loss are not always benign inner ear problems. When these symptoms arise suddenly from a stroke, they indicate damage to the brainstem, the auditory pathways, or the blood vessels supplying them. The lateral medullary syndrome, AICA territory stroke, SCA territory stroke, and basilar artery occlusion each produce distinct patterns of central vertigo and, in the case of AICA, frank hearing loss. Recognising these patterns can mean the difference between a missed brainstem stroke and timely, lifesaving treatment.