Review Question - QID 216992

This patient is presenting with left-sided lateral pontine syndrome as evidenced by 7th cranial nerve dysfunction (facial asymmetry and abnormal taste sensation), decreased ipsilateral face and contralateral body pain and temperature sensation, ipsilateral Horner syndrome (miosis and ptosis), and ataxia. This constellation of symptoms is seen with a left-sided lateral pontine infarct, which is caused by an occlusion of the anterior inferior cerebellar artery.

Strokes of the brainstem can be particularly detrimental due to numerous key nuclei and spinal cord tracts that are present in the region. Occlusion of the anterior inferior cerebellar artery can lead to infarction of the lateral pons. Symptoms are linked to the affected tracts and nuclei: vestibular nuclei (vertigo), spinothalamic tract (decreased pain and temperature in the contralateral body), spinal trigeminal nucleus (decreased pain and temperature in the ipsilateral face), sympathetic fibers (Horner syndrome), and facial nucleus (facial paralysis, decreased taste from anterior 2/3 tongue, salivation, and lacrimation). As with any stroke, primary prevention by reduction of modifiable risk factors (high blood pressure, smoking, dyslipidemia, and diabetes) is critical because damage from infarction is permanent.

Oh et al. explored the relationship between specific pontine infarction location and progressive motor deficits. In their logistic multiple regression analysis, they found lower pontine lesions were a risk factor for worsening motor deficits. Hypertension and female sex were also found to be risk factors.

Incorrect Answers:
Answer 1: The anterior cerebral artery (ACA) supplies the medial portions of the frontal lobes and superior parietal lobes. An ACA infarct can present with contralateral weakness and sensory loss of the lower extremities, abulia (lack of will), and gait apraxia.

Answer 3: The basilar artery supplies large areas of the brainstem including the caudal midbrain, ventral pons, and medulla. Infarction of the basilar artery can cause locked-in syndrome. Due to the involvement of corticospinal/corticobulbar tracts, oculomotor nerve nuclei, and the paramedian pontine reticular formation, the patient becomes quadriplegic and unable to speak while retaining consciousness; only vertical eye movements are normally retained.

Answer 4: The lenticulostriate artery supplies the basal ganglia. Its infarct has a variety of presentations: pure motor weakness, pure sensory weakness, ataxic hemiparesis, and dysarthria-clumsy hand syndrome. In contrast to anterior and middle cerebral artery strokes, there are no cortical signs (e.g., aphasia, neglect, agraphia, extinction, etc.).

Answer 5: The posterior inferior cerebellar artery (PICA) supplies the lateral medulla. Infarction of the PICA causes lateral medullary syndrome (also known as Wallenberg syndrome). Lateral medullary syndrome shares many similarities with lateral pontine syndrome, namely involvement of the vestibular nuclei, spinothalamic tract, spinal trigeminal nucleus, and sympathetic fibers. However, a PICA infarct affects the nucleus ambiguus, leading to abnormalities of the glossopharyngeal nerve (dysphagia, hoarseness and decreased gag reflex).

Bullet Summary:
An anterior inferior cerebellar artery infarct affects the lateral pons, which may result in vertigo, decreased contralateral body and ipsilateral face pain and temperature, Horner syndrome, and facial nerve dysfunction.