A 7-year-old girl experienced difficulty walking for 3 days, left eye esotropia, double vision, and speech impairment. She reported a headache for the preceding 2 weeks. She was the second child of nonconsanguineous parents and had no significant past medical history. Her 12-year-old brother was healthy.

Physical examination revealed temperature of 36.4°C, pulse 96, blood pressure 95/65, weight 22 kg (40%), and height 123 cm (58%). Examination of respiratory, cardiovascular, gastrointestinal, and genitourinary systems were unremarkable. No birthmarks were noted. Neurological examination revealed a conscious and cooperative patient without signs of meningeal irritation. She had limited lateral left gaze indicating a sixth nerve palsy. She also had left central seventh nerve palsy with lower facial paralysis and normal forehead movements. Speech was dysarthric. Dysmetria and dysdiadochokinesia were present. Gait was broad-based and ataxic. Romberg test was positive.

Routine laboratory testing was normal.

Brain MRI showed an expansile nonenhancing tumor infiltrating nearly the entire pons, without associated enhancement or diffusion restriction. There was partial encasement of the basilar artery and effacement of the floor of fourth ventricle. MRS was suggestive of low-grade neoplasia ( Fig. 44.1 ).

Diffuse intrinsic pontine glioma. Brain MRI, (A) axial FLAIR shows a hyperintense expansile pontine mass with effacement of the floor of fourth ventricle dorsally ( black arrow ) and partial encasement of basilar artery ventrally ( white arrow ). (B) Sagittal postcontrast T1 shows no appreciable enhancement. (C) Axial DWI shows no diffusion restriction. (D) MRS (TE = 135 ms) shows moderate lactate peak ( arrow ), increased choline (Cho), and decreased NAA. DWI , Diffusion-weighted imaging; FLAIR , Fluid-attenuated inversion recovery; MRS, magnetic resonance spectroscopy; NAA , N-acetylaspartate.

Brainstem and cerebellar dysfunction raise concern for posterior fossa disorders, including neoplastic, infectious, demyelinating or autoimmune, vascular, and traumatic pathologies.

Brainstem tumors include diffuse intrinsic pontine glioma (DIPG), lymphoma, hemangioblastoma, germ cell tumors, and gliomas.

Inflammatory conditions such as Langerhans cell histiocytosis can affect the posterior fossa with variable enhancement and white matter signal changes.

Autoimmune disorders such as Behçet disease and Bickerstaff encephalitis can preferentially affect the brainstem.

Infectious rhombencephalitis can be related to viral, bacterial, and parasitic pathogens.

Osmotic demyelination classically affects the central pons with sparing of the periphery and corticospinal tracts. Extrapontine myelinolysis can affect the basal ganglia and supratentorial white matter tracts. This occurs with rapid correction of hyponatremia or other systemic imbalances.

Patients with genetic disorders, such as neurofibromatosis type 1 or tuberous sclerosis, may develop dysplastic lesions in the brainstem and cerebellum.

Vascular malformations, such as cavernous malformations or arteriovenous malformations, can have central hemorrhage/enhancement and surrounding edema.

Diffuse intrinsic pontine glioma/diffuse midline glioma.