The brain stem consists of the midbrain, pons, and medulla. Brain stem infarction commonly occurs due to an embolus occluding large arteries (vertebral or basilar arteries) supplying it or due to an embolus traveling from the heart, or atherosclerotic plaques from the large arteries (vertebral, basilar) [1]. Brainstem infarcts are relatively less common as compared to hemispheric infarcts [2]. The common clinical presentation is sudden onset focal neurological deficits like hemiparesis, vertigo, orthostatic symptoms, diplopia, and lower cranial nerve paralysis with dysphagia, and hoarseness. Vertigo is the cardinal feature of brain stem infarction [2] followed by ipsilateral cranial nerve symptoms, contralateral hemiplegia, hemianesthesia (crossed motor or sensory signs) with bilateral involvement of the sensory tract or motor tract or both.

A few uncommon clinical features of brain stem infarction include "salt and pepper" facial pain [3], blepharospasm [4], palatal myoclonus [2], hiccough [5], tinnitus in medullary infarction [6], bruxism and trismus in basilar artery occlusion [7], and peduncular hallucinosis in midbrain infarction [8]. If there is total occlusion of the vertebrobasilar system then patients can present with tachycardia, fluctuating blood pressure, ataxia, impaired consciousness, and coma leading to death. Pontine or midbrain infarction can also present as "locked-in syndrome" in which the affected individual has sudden onset vomiting, transient loss of consciousness with quadriplegia, bilateral facial palsy, anarthria (total loss of articulation), and bilateral oculomotor nerve palsy resulting in loss of voluntary eye movements [2].

Clinical features specific to the ischemic involvement of the different regions of the brainstem are:

Midbrain: ipsilateral oculomotor (3rd cranial nerve) paralysis with contralateral hemiplegia (Weber syndrome)

Pons: 5th, 6th, 7th and 8th cranial nerve involvement, diplopia, dysarthria, vertigo, gait abnormality, and/or sensation of ear canal block, sustained horizontal nystagmus, conjugate eye movements when the gaze is directed towards the side of hemiparesis [6], ataxic hemiparesis.

Medulla: 9th, 10th, 11th and 12th cranial nerve involvement, pure motor hemiparesis if the medullary pyramid is the site of the infarction; sensory motor hemiplegia if the medial lemniscus is involved; or Dejerine syndrome wherein there is ipsilateral tongue paralysis with contralateral hemiplegia. A patient presenting with acute onset vertigo and then developing sudden respiratory failure is likely to have a medullary infarct.

• Periodic Breathing

  Oku Y, Okada M (2008) Periodic breathing and dysphagia associated with a localized lateral medullary infarction. Respirology (Carlton, Vic.) 13: 608–610. View Article Google Scholar 57. [journals.plos.org]

• Respiratory Abnormalities

  Abstract The distribution of tyrosine hydroxylase (TH) and substance P (SP) was examined in the brain-stem of 4 infants with respiratory abnormalities associated with remote brain-stem or cerebellar infarction utilizing immunohistochemical methods. [ncbi.nlm.nih.gov]

• Bruxism

  A few uncommon clinical features of brain stem infarction include "salt and pepper" facial pain, blepharospasm, palatal myoclonus, hiccough, tinnitus in medullary infarction, bruxism and trismus in basilar artery occlusion, and peduncular hallucinosis [symptoma.com]

• Miosis

  Neurological examinations showed left ptosis and miosis, hoarseness, dysphagia, right mild hemiparesis, left ataxia of his extremities, and truncal ataxia. He also had hypalgesia/hypotemperature on his right side. [hindawi.com]

  It is typified by vertigo, ipsilateral hemiataxia, dysarthria, ptosis and miosis. Most patients with this stroke recover very well and often resume their previous activities (Nelles et al, 1998). [tchain.com]

  […] the distribution of the 5th cranial nerve (this nucleus is a long vertical structure that extends in the lateral aspect of the pons down into the medulla) Sympathetic pathway : ipsilateral Horner’s syndrome, that is partial ptosis and a small pupil (miosis [lifeinthefastlane.com]

  Ipsilateral clinical features include the following: Ataxia and dysmetria, due to damage to the inferior cerebellar peduncle and cerebellum Horner syndrome (eg, ptosis, miosis, hypohidrosis or anhidrosis, enophthalmos), due to damage to descending sympathetic [emedicine.medscape.com]

• Ciliary Injection

  Slit-lamp examination showed ciliary injection and keratic precipitates. Fundus examination demonstrated vasculitis in both eyes (Figures 1(a) and 1(b)). Physical examination showed exudative erythema nodosum on his trunk and both thighs. [hindawi.com]

• Dizziness

  Two days after discharge from the hospital he was admitted to the neurological department in the university hospital with dizziness, hickups, reduced sensitivity of the right side of face and trunk. [relis.no]

  Two days after his first visit, he reported dizziness, speech disturbance, clumsiness of his right extremities, and gait disturbances. [hindawi.com]

  Dizziness. You may feel too dizzy to stand up. Weakness or numbness in your arm, leg, or face. This may happen on only one side of your body. Confusion, or trouble speaking. Unable to see out of one or both of your eyes. Copyright 2011. [drugs.com]

  A person may have vertigo, dizziness and severe imbalance without the hallmark of most strokes — weakness on one side of the body. The symptoms of vertigo dizziness or imbalance usually occur together; dizziness alone is not a sign of stroke. [stroke.org]

• Nystagmus

  […] oculomotor (3rd cranial nerve) paralysis with contralateral hemiplegia (Weber syndrome) Pons: 5th, 6th, 7th and 8th cranial nerve involvement, diplopia, dysarthria, vertigo, gait abnormality, and/or sensation of ear canal block, sustained horizontal nystagmus [symptoma.com]

  In the author's experience, these patients often exhibit rebound nystagmus, which is a variant of gaze-evoked nystagmus. Some of these patients have upbeating nystagmus supine, often confused with BPPV. [dizziness-and-balance.com]

  Acute onset in an unknown diabetic associated with brain-stem infarction and death. ( 4212098 ) Siegel A.J....Bell W.R. 1974 43 See-saw nystagmus: an unusual sign of brain-stem infarction. ( 4847304 ) Mastaglia F.L. 1974 44 Sleep patterns in a patient [malacards.org]

  In the author's experience, these patients often exhibit rebound nystagmus, which is a variant of gaze-evoked nystagmus. [tchain.com]

• Cranial Nerve Involvement

  Medulla: 9th, 10th, 11th and 12th cranial nerve involvement, pure motor hemiparesis if the medullary pyramid is the site of the infarction; sensory motor hemiplegia if the medial lemniscus is involved; or Dejerine syndrome wherein there is ipsilateral [symptoma.com]

  Clinically, in localizing strokes to the brainstem one looks for the "cardinal" feature of an ipsilateral peripheral cranial nerve involvement, and a contralateral weakness or sensory deficit. Cerebellar signs, if present, should be ipsilateral. [tchain.com]

  Contra pain and temp Vascular - Pica or vertebral Symptoms of brainstem stroke Clinically, in localizing strokes to the brainstem one looks for the "cardinal" feature of an ipsilateral peripheral cranial nerve involvement, and a contralateral weakness [dizziness-and-balance.com]

• Stupor

  Postoperative stupor and coma. Mayo Clin Proc. 2005 Mar;80(3):350-4. [clinicclinic2.cafe24.com]

  However, this trial did not include patients in stupor or coma, and that criterion probably excluded patients who suffered a basilar artery occlusion. Moreover, the trial did not study the vascular anatomy systematically in all patients. [emedicine.medscape.com]

• Altered Mental Status

  Patients with bilateral VAI usually presented with more severe symptoms, including an altered mental status, pinpoint pupils, and even sudden respiratory arrest [6, 12, 16, 17]. Occasionally, bilateral VAI patients remain asymptomatic [1, 2, 18]. [pssjournal.biomedcentral.com]

The aim of the workup is to determine the characteristics of the vascular lesion and the etiology of the brain stem infarction. A detailed history during workup provides clues to the risk factors and etiology of the condition while a thorough neurological, cardiovascular, and bedside glucose testing are mandatory to determine further workup and management.

Computed tomography scanning (CT) is performed first to differentiate between an ischemic infarct and hemorrhagic stroke as it has 95% sensitivity in identifying hemorrhage especially if done within 24 hours of onset of symptoms [9] [10]. Occluded and dolichoectatic arteries can be identified better with spiral CT angiography [11] [12]. Magnetic resonance imaging (MRI) has greater sensitivity than CT in the identification of ischemia with small lacunar infarcts being seen only on MRI. Diffusion-weighted MRI is highly sensitive for early ischemia and should be ordered after the CT scan. MRI and magnetic resonance angiography (MRA) are useful in detecting dissection, demyelinating plaques, vertebrobasilar dolichoectasia, and dissection. [13] [14] [15].

In addition, other tests are indicated based on the clinical evaluation to detect the etiology and risk factors of the brainstem infarct:

Cardiac factors: electrocardiography (in all cases), telemetry or holter monitoring, serum troponin (in cases suspected to have myocardial ischemia), and echocardiography [16] especially in patients under 45 years of age or in those with basilar artery occlusion.

Vascular factors: blood tests to rule out thrombotic disorders (homocysteine levels, antiphospholipid antibodies, protein S, protein C, antithrombin III, factor V Leiden) and routine tests like complete blood count, platelet count, PT/PTT, fasting blood glucose, lipid profile, and serology for syphilis.

Autoimmune factors: antinuclear antibodies, rheumatoid factor, erythrocyte sedimentation rate.

Urine toxicology and drug screening for stimulants like cocaine and amphetamines.

• Treponema Pallidum

  Studies for young stroke showed positive rapid plasma reagin (RPR) (1:32), positive treponema pallidum haemagglutination ( 1:1280), positive anti-HIV antibody and confirmed with western blot. [academic.oup.com]

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