To the Editor: Bilateral medial medullary infarction (MMI) is a rare stroke subtype. It usually leads to quadriplegia, sensory disturbance, hypoglossal palsy, bulbar paralysis, etc. We encountered a patient with rapidly progressive tetraparesis and diffusion-weighted imaging (DWI) exhibited a “heart appearance” sign in the bilateral ventral medulla. Computed tomography angiography (CTA) demonstrated that the left vertebral artery (VA) was hypoplastic and there was an atherosclerotic stenosis in the V4 segment.
Two days prior to admission, a 54-year-old man suddenly suffered from dizziness in the morning, followed by somnolence in the afternoon. During the night, he developed mild left-sided weakness and slurred speech at 11 PM. On the following day, the patient worsened into a rapidly progressive tetraparesis. He had a history of hypertension and diabetes. Neurologic examination revealed dysarthria, flaccid quadriplegia, bilateral Babinski signs without nystagmus, tongue paralysis or sensory disturbance. Pupils and eye movements were normal. The power in his four limbs was 0 of 5. Brain magnetic resonance images obtained 1 day after symptom onset showed a slight hyperintensity in the bilateral anteromedial medulla on axial T2-weighted imaging. DWI exhibited a hyperintense “heart appearance” signal in the corresponding area [Figure 1A]. CTA showed the left VA was wholly slenderer than the contralateral side in the extracranial portion and there was an atherosclerotic stenosis in the V4 segment [Figure 1B]. The patient was treated with aspirin and atorvastatin. On the second day of admission, he received tracheotomy due to dyspnea. The power in his four limbs was still 0 of 5 after 2 weeks in hospital and then the patient was transferred to the rehabilitation hospital. He had a modified Rankin Scale score of four at 3 months after symptom onset.
MMI accounts for less than 1% of ischemic strokes and bilateral MMI is even rarer. The “heart appearance” sign in the ventral medulla on axial DWI is a characteristic imaging finding of bilateral MMI. The common clinical manifestations of bilateral MMI include flaccid quadriplegia, loss of deep sensation, dysarthria, nystagmus, hypoglossal palsy, respiratory failure, etc. This patient is a rare case of pure motor quadriplegia and bulbar dysfunction, and different symptom combinations of bilateral MMI usually depend on the location and extent of the lesion.
A recent systematic review showed that the most common mechanisms of bilateral MMI include large-artery atherosclerosis and small penetrating artery disease. In this case, CTA showed atherosclerotic stenosis at distal portion of the left VA. The underlying mechanisms of bilateral MMI with unilateral VA stenosis are as follows: (1) anatomic variability of perforator branches that supply the bilateral medulla, (2) the extension of thrombus in the vertebrobasilar junction to the contralateral side and (3) bilateral anterior spinal artery originating from the same pathological VA.[2,4]
It is worth noting that the responsible vessel of VA was hypoplastic in this case. Vertebral artery hypoplasia (VAH) is a common congenital anatomical variation and it may contribute to posterior circulation strokes. The ischemic lesions with VAH mainly present in posterior inferior cerebellar artery territory, posterior cerebral artery territory, and pons, while the presentation in bilateral medial medulla is rare.
In summary, the patient with bilateral MMI may present pure motor quadriplegia and clinicians should be aware that the distal stenosis of unilateral hypoplastic VA may be one of the vascular pathologies of bilateral MMI.
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Conflicts of interest
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