Temporal bone and cranial nerve findings in pontine tegmental cap dysplasia

Abstract

Patients with PTCD have highly characteristic temporal bone and cranial nerve findings on both CT and MR. Recognition of these findings is important for improved diagnosis of this rare disorder, particularly by CT.

Clinicoradiological aspects of pontine tegmental cap dysplasia: Case report of a rare hindbrain malformation

“…In the largest reported series of 16 patients reviewed retrospectively and published recently in 2016 by Nixon et al ., the authors found associated duplication of one or both internal auditory canals in all but one patient. [ 8 ] Associated cochlear nerve aplasia and either atresia or stenosis of internal auditory canals was also observed in their study. However, our patient did not reveal any temporal bone and cochlear nerve abnormality.…”

Pontine tegmental cap dysplasia accompanied by a duplicated internal auditory canal

“…PTCD is a brainstem malformation ( 1 , 3 , 4 ) , initially described in 2007 by Barth et al ( 5 ) ; to date, fewer than 50 cases have been reported ( 4 ) . The main signs and symptoms are auditory deficiency, in 92% of cases; cognitive deficit, in 76%; deglutition disorders, in 64%; facial paralysis, in 60%; abnormal eye movement, in 60%; trigeminal paresthesia, in 60%; ataxia, in 56%; hypotonia; cyclic vomiting syndrome; and various neurological disorders of the third to the eighth cranial nerves ( 4 , 6 , 7 ) .…”

“…PTCD is a brainstem malformation ( 1 , 3 , 4 ) , initially described in 2007 by Barth et al ( 5 ) ; to date, fewer than 50 cases have been reported ( 4 ) . The main signs and symptoms are auditory deficiency, in 92% of cases; cognitive deficit, in 76%; deglutition disorders, in 64%; facial paralysis, in 60%; abnormal eye movement, in 60%; trigeminal paresthesia, in 60%; ataxia, in 56%; hypotonia; cyclic vomiting syndrome; and various neurological disorders of the third to the eighth cranial nerves ( 4 , 6 , 7 ) . Other potential characteristics of PTCD include hypoplasia of the pons (notably in its ventral aspect); a mass of ectopic dorsal pontine fibers protruding into the fourth ventricle; hypoplasia/agenesis of the middle and inferior cerebellar peduncles; elongation of the superior cerebellar peduncles; cerebellar vermis hypoplasia/ agenesis; absence or malformation of the inferior olivary nuclei; hypogenesis/absence of the third to eighth cranial nerves; costovertebral deformities; and cardiovascular anomalies ( 1 , 3 - 8 ) .…”

“…Other potential characteristics of PTCD include hypoplasia of the pons (notably in its ventral aspect); a mass of ectopic dorsal pontine fibers protruding into the fourth ventricle; hypoplasia/agenesis of the middle and inferior cerebellar peduncles; elongation of the superior cerebellar peduncles; cerebellar vermis hypoplasia/ agenesis; absence or malformation of the inferior olivary nuclei; hypogenesis/absence of the third to eighth cranial nerves; costovertebral deformities; and cardiovascular anomalies ( 1 , 3 - 8 ) . PTCD can exhibit a feature similar to the molar tooth sign, although with lateralized, tapered superior cerebellar peduncles ( 1 , 4 , 6 ) . The differential diagnoses include pontocerebellar hypoplasia, as well as a number of syndromes ( 2 , 8 , 9 ) : Joubert; Dekaban-Arima; Senior-Loken; COACH; Váradi-Papp; Malta; and Moebius.…”

“…Although a duplicated internal auditory canal is extremely rare, it is found in at least 46% of all cases of PTCD. The two canals are often narrow (with a caliber of less than 2.0 mm) and accompanied by hypogenesis/agenesis of the eighth cranial nerve, which typically contraindicates cochlear implantation ( 4 , 8 , 10 , 11 ) . Some authors have reported differentiated cases in which the division is made by a bony septum, proposing that the term "partitioned" (rather than "duplicated") be used in such cases ( 11 ) .…”