Kinked brainstem

Last revised by Owen Kang on 2 Feb 2019

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.

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).

A kinked brainstem has been reported in association with:

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

  2. tubulinopathy (TUBA1A mutation)

  3. X-linked hydrocephalus (L1CAM mutation)

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:

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

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