Pontine tegmental cap dysplasia (PTCD) is a rare congenital malformation of the brainstem and hindbrain with imaging hallmark of an ectopic dorsal transverse pontine fiber projecting from the tegmentum into the fourth ventricle hence the name PTCD1.
PTCD is a rare congenital malformation with just over 20 reported cases in the literature 1. Actual prevalence may be underestimated due to failure to recognise the disease entity or mis-classification.
Patients present with developmental delay, cerebellar and pyramidal abnormalities, cranial nerve (V, VII, VIII and XII) dysfunction leading to neurosensorial hearing loss, swallowing impairment and oculomotor palsy 3,6.
To date no specific mutations were identified 1.
- HRCT temporal bone may demonstrate duplicated internal auditory canal associated with VII/VIII nerve hypoplasia and aplasia 4
MRI is best imaging modality to characterise the structural abnormality 1-2,6:
- ectopic dorsal transverse pontine fiber projecting from the tegmentum into the fourth ventricle. On diffusion tensor imaging (DTI) the ectopic fiber can be visualised as horizontally directed fiber (colour coded red) arising from the pontine tegmentum 2
- hypoplasia and aplasia of the middle cerebellar peduncle
- variable hypoplasia of the inferior cerebellar peduncle
- lateralised course of the superior cerebellar peduncle resulting in "molar tooth" appearance of the midbrain
- variable supratentorial abnormality which is non-specific to this condition (e.g. ventriculomegaly)
- high resolution T2 weighted sequence is useful to detect cranial nerve abnormality such as V, VI, VII and VIII hypoplasia and aplasia 4-6
History and etymology
It was first described by Barth et al. in 2007.
- 1. Barth PG, Majoie CB, Caan MW et-al. Pontine tegmental cap dysplasia: a novel brain malformation with a defect in axonal guidance. Brain. 2007;130 (Pt): 2258-66. doi:10.1093/brain/awm188 - Pubmed citation
- 2. Jissendi-tchofo P, Doherty D, Mcgillivray G et-al. Pontine tegmental cap dysplasia: MR imaging and diffusion tensor imaging features of impaired axonal navigation. AJNR Am J Neuroradiol. 2009;30 (1): 113-9. doi:10.3174/ajnr.A1305 - Pubmed citation
- 3. Rauscher C, Poretti A, Neuhann TM et-al. Pontine tegmental cap dysplasia: the severe end of the clinical spectrum. Neuropediatrics. 2009;40 (1): 43-6. doi:10.1055/s-0029-1224100 - Pubmed citation
- 4. Desai NK, Young L, Miranda MA et-al. Pontine tegmental cap dysplasia: the neurotologic perspective. Otolaryngol Head Neck Surg. 2011;145 (6): 992-8. doi:10.1177/0194599811412729 - Pubmed citation
- 5. Singh D, Hsu CC-T, Kwan GNC, Korah I. Pontine Tegmental Cap Dysplasia: MR Evaluation of Vestibulocochlear Neuropathy. Journal of Neuroimaging. Article first published online: 17 FEB 2015 | DOI: 10.1111/jon.12209 http://www.ncbi.nlm.nih.gov/pubmed/25691269
- 6. Bosemani T, Orman G, Boltshauser E et-al. Congenital abnormalities of the posterior fossa. Radiographics. 2015;35 (1): 200-20. doi:10.1148/rg.351140038 - Pubmed citation