Dorsal brainstem syndrome

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

Terminology

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

Pathology

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

Clinical presentation

Injuries involving the tegmentum of the caudal pons and medulla will result in compromising several vital functions as it harbors 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.

Imaging features

MRI

• T1: Bilateral symmetrical hypointensity involving tegmentum of caudal pons and medulla
• 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 hyperglycinemia and mitochondrial injury ^9,10.