kinked brainstem

Radiopaedia • CC-by-nc-sa 3.0 • de

Kinking of the brainstem is a rare finding in fetal or pediatric neuroimaging, invariably seen in association with other cerebral abnormalities. It generally heralds a poor neurological outcome.

Clinical presentation

A kinked brainstem may be seen on fetal MRI, commonly after referral from ultrasound with ventriculomegaly +/- other intracranial abnormalities.

Alternatively, it may be detected on MRI of a neonate presenting with a poor neurologic state, hypotonia, seizures, abnormal visual examination or abnormality of head size (micro or macrocephaly).

Etiology

A kinked brainstem has been reported in association with:

  • a-dystroglycanopathies (including Walker-Warburg syndrome, muscle-eye-brain disease)

  • tubulinopathy (TUBA1A mutation)

  • X-linked hydrocephalus (L1CAM mutation)

    • Radiographic Features

    Kinking of the brainstem refers to an exaggerated flexure at the pontomesencephalic junction.

    There is a wide range of associated findings. Cerebellar hypogenesis is almost always seen. Other findings include:

    Practical Points

    When a kinked brainstem is detected with ventriculomegaly on prenatal MRI, an attempt should be made to distinguish between the three possible causes, to direct genetic testing and counseling.

    • L1CAM mutation suggested with
      • male fetus
      • non-visualization of cerebral acqueduct high T2 signal (though this should be interpreted cautiously, as small fetal size and motion may produce a false positive finding) 
      • spasticity and adduction of thumbs (best seen on ultrasound dynamically)
      • NO abnormality of globes or ganglionic eminences
    • dystroglycanopathy
      • cobblestone lissencephaly suggests Walker-Warburg syndrome (often difficult to detect in the fetus due to stretching of brain parenchyma by ventriculomegaly)
      • enlarged ganglionic eminences
      • encephalocele not diagnostic but suggestive
      • ocular abnormalities (persistent hyperplastic primary vitreous (PHPV), microphthalmia, buphthalmos, retinal detachment) strongly suggestive, though may not be visible prenatally
    • tubulinopathy
      • enlarged ganglionic eminences