The spectrum of brainstem malformations associated to mutations of the tubulin genes family: MRI and DTI analysis

OBJECTIVES:
To describe the spectrum of brainstem malformations associated to mutations in the tubulin genes taking advantage of magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI).

METHODS:
Fifteen patients (six males; median age, 1.25 years; range, 1 month to 31 years) with mutations in the tubulin genes (TUBA1A = 8, TUBB2B = 4, TUBB3 = 3) studied with MRI and DTI were included in the study. Brain MR exams were reviewed to describe the malformative aspects of the brainstem. Malformations of the supratentorial brain and cerebellum were also recorded. Tractography was performed in seven selected cases.

RESULTS:
Fourteen patients (93%) showed complex malformations of the brainstem. Most common findings, apparent on anatomical MR sequences, were brainstem asymmetry (12 cases, 5 of which with a crossed pattern characterised by a hypertrophic right medulla oblongata and hypertrophic left pons), short and small pons on midline (10 cases) and anterior brainstem clefting (6 cases). DTI revealed abnormal transverse pontine fibres (13 cases), fusion of corticospinal tracts and medial lemnisci (9 cases) and a small decussation of the superior cerebellar peduncles (7 cases).

CONCLUSIONS:
Conventional/anatomical MRI and DTI reveal a complex pattern of brainstem malformations associated with tubulin genes mutations.