Dorsal brainstem syndrome

Dorsal brainstem syndrome is a rare subset of hypoxic ischaemic encephalopathy in neonates limited to the isolated involvement of the brainstem with sparing of the supratentorial brain. Due to its subtle imaging features, it is often undiagnosed.

Clinical presentation

Injuries involving the tegmentum of the caudal pons and medulla will result in compromising several vital functions as it harbours cranial nerve nuclei of the cranial nerves VI, VII, X, XII. They may present with bilateral facial nerve palsy, impaired sucking, swallowing, hypotonia, seizure and psychomotor delay ^3,8.

Pathology

Isolated bilateral symmetrical lesions of the brainstem tegmentum in the region of caudal pons and medulla oblongata with clinical features supportive of brainstem injury in hypoxic ischaemic infants are described under dorsal brainstem syndrome ¹. Neonates with less severe birth asphyxia have brainstem with lesions in the tegmentum even in the absence of supratentorial lesions ^2-6.

The tegmentum represents the watershed territory of the brainstem predominantly supplied by the branches of the vertebrobasilar system and less compensated by the anterior circulation making it vulnerable to hypoxic and hypotensive insults ⁷.

Radiographic features

MRI

• T1: bilateral symmetrical hypointensity involving tegmentum of caudal pons and medulla, no obvious signal changes in the supratentorial brain
• T2: bilateral symmetrical hyperintensity involving tegmentum of caudal pons and medulla, no obvious signal changes in the supratentorial brain

Differential diagnosis

Tegmental lesions are also demonstrated in infants with metabolic disorder including hyperglycinaemia and mitochondrial injury ^9,10.