CASE 18573 Published on 31.05.2024

A rare type of cerebrovascular accident

Section

Neuroradiology

Case Type

Clinical Case

Authors

Madhu S. Kikkeri, Vidhya Rani R., Naveena G., Siripurapu Vinaya Ratna

Department of Radiodiagnosis, Sapthagiri Institute of Medical Sciences and Research Centre, Bengaluru, Karnataka, India

Patient

77 years, male

Categories
Area of Interest Neuroradiology brain ; Imaging Technique MR
Clinical History

A 77-year-old man with hypertension and type 2 diabetes, presented with bilateral upper and lower limb weakness and dyspnoea. He was intubated at a nearby hospital and referred to us for further management. At admission, he was drowsy with Glasgow Coma Scale (GCS) of E4M1VT. He was admitted to the ICU and put on mechanical ventilator, and a nasogastric tube was inserted. An initial CT-Brain was done, which was unremarkable, followed by an MRI Brain.

Imaging Findings

MRI Brain with 1.5 Tesla superconducting magnet was performed on the same day, which revealed a T2 and FLAIR hyperintense (Figures 1a and 1b) area showing true diffusion restriction (Figures 2a and 2b) in the bilateral medial medulla, extending to the lower pons (Figure 3), consistent with an acute infarct. The lesion involved the medial medulla bilaterally, mainly in the ventral half, with partial extension dorsally, giving a characteristic “heart sign” on axial sections (Figures 1a, 1b, 2a, 2b, and 4). TOF-MR angiography was normal. Supratentorial brain parenchyma showed cerebral atrophy with chronic small vessel ischemic changes.

Discussion

Background

Stroke is the world’s second-largest cause of death and a major cause of disability. Ischemic stroke is more frequent and less morbid than haemorrhagic strokes [1]. 20–25% of all acute strokes occur in the posterior circulation and are difficult to diagnose because of diverse presentation, which can be mistaken for more benign entities [2]. Medial medullary infarction (MMI), involving medial medullary structures, accounts for only less than 1–1.5% of ischemic strokes in the posterior circulation, in which bilateral infarctions are even rare. Bilateral MMI (BMMI) usually arises from atherothrombotic processes affecting either the vertebral artery or the anterior spinal artery (ASA). Prolonged thrombosis coupled with the anatomical diversity of paramedian branches originating from them, or the possibility of a single paramedian artery supplying both pyramids, could explain the simultaneous bilateral infarctions, despite a single-sided artery affection [3].

Clinical Perspective

While posterior circulation strokes typically manifest with crossed deficits (ipsilateral cranial nerve and contralateral extremity (motor or sensory), this presentation lacks sensitivity. Thus, maintaining a high clinical suspicion and promptly utilising imaging is crucial for accurate diagnosis and treatment [2]. Infarction of medial medullary structures (lateral corticospinal tract, medial lemniscus, and hypoglossal nerve) leads to contralateral paralysis of the upper and lower limbs, contralateral decrease in sensation and ipsilateral deviation of the tongue due to ipsilateral hypoglossal nerve damage (the lower motor neuron type) [4]. Dysarthria and respiratory distress due to the proximity of the hypoglossal nerve and medullary respiratory centre may also occur [2]. The main cause of death in BMMI is respiratory infection [5].

Imaging Perspective

The “heart sign” is a classic radiological finding in axial sections of MRI in BMMI due to the symmetric affection of the pyramids, separated by the anterior median fissure. Only two-thirds of cases with BMMI will present with the “heart sign” in the first 24 hours. Initial changes are seen only in DWI and ADC sequences [2]. Atypical MRI findings include faint or delayed DWI changes [6] or an incomplete “heart sign” in two consecutive axial sections [3]. On account of complex vascular networks supplying the medial medulla and the spatial resolution limitation of MRA, it is commonly difficult to identify the occluded culprit vessel on MR angiography, and thus TOF-MRA may be normal [3]. Due to its symmetrical and midline appearance, resembling an artefact, certain radiologists might overlook this particular type of stroke [6].

Outcome

In our case, thrombolysis was not done as the patient presented outside the window for thrombolysis. Further, as there was no large vessel occlusion, thrombectomy was deferred. Conservative management was given with aspirin, oral hypoglycemic, antihypertensives and physiotherapy was advised. At the time of discharge, patient did not show much improvement from his presentation.

Take Home Message

BMMIs are very rare and are associated with catastrophic consequences, if not diagnosed early. Diagnosing it without neuroimaging is very difficult. This case report serves to raise awareness about the clinicoradiological correlation and typical imaging findings in this very rare type of stroke.

Written informed patient consent for publication has been obtained.

Differential Diagnosis List
Bilateral medial medullary infarction
Final Diagnosis
Bilateral medial medullary infarction
Case information
URL: https://www.eurorad.org/case/18573
DOI: 10.35100/eurorad/case.18573
ISSN: 1563-4086
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