Temporal bone and cranial nerve findings in pontine tegmental cap dysplasia

Pontine tegmental cap dysplasia: the role of diffusion tensor imaging

Pontine tegmental cap dysplasia (PTCD) is a rare hindbrain malformation syndrome. Recurrent aspiration pneumonia is a major cause of death during a first year of life. We report the case of month-old child with an inability to suck milk since birth and multiple convulsions. PTCD was identified using tractography and MRI. This case report describes the imaging findings, the role of diffusion tensor imaging in PTCD and its differentiating features from Joubert syndrome and related disorders (JSRDs). The constellation of imaging features in PTCD includes a midbrain appearance resembling a molar tooth, a flattened anterior pontine belly, hypoplastic middle cerebellar peduncles and dorsal pontine tegmental cap. 'Tegmental cap' is a transversely oriented abnormal bundle of fibres with absent superior cerebellar peduncle decussation. Accurate diagnosis with MRI and tractography and differentiating PTCD from JSRD would help the clinician for appropriate genetic counselling and prognosis.

Congenital Brain Malformations: An Integrated Diagnostic Approach

Congenital brain malformations are abnormalities present at birth that can result from developmental disruptions at various embryonic or fetal stages. The clinical presentation is nonspecific and can include developmental delay, hypotonia, and/or epilepsy. An informed combination of imaging and genetic testing enables early and accurate diagnosis and management planning. In this article, we provide a streamlined approach to radiologic phenotyping and genetic evaluation of brain malformations. We will review the clinical workflow for brain imaging and genetic testing with up-to-date ontologies and literature references. The organization of this article introduces a streamlined approach for imaging-based etiologic classification into malformative, destructive, and migrational abnormalities. Specific radiologic ontologies are then discussed in detail, with correlation of key neuroimaging features to embryology and molecular pathogenesis.

Ocular Findings in Pontine Tegmental Cap Dysplasia

PURPOSE

To describe the ocular complications experienced by patients with pontine tegmental cap dysplasia (PTCD) and the management strategies used to care for these children.

METHODS

Subjects with PTCD were recruited through social media advertisement and completed a survey gathering information on potential ocular problems related to the patient's PTCD disease and any current or previous treatments.

RESULTS

Twenty-two patients or guardians completed the survey. Neurotrophic cornea was the most common ocular diagnosis (82%), followed by facial palsy (59%), dry eye syndrome (59%), and blepharitis (55%). Other diagnoses included cortical visual impairment (27%), strabismus (27%), amblyopia (18%), and nystagmus (18%). Common treatment modalities included lubricating eye drops (59%) or ointment (50%), contact lenses (14%), punctal plugs (27%), glasses (45%), and patching (18%). The most common surgical interventions were temporary or permanent tarsorrhaphy (64%) and amniotic membrane grafts (23%). In total, 68% of families reported self-injury to eyes and 91% reported the child to be primarily a visual learner.

CONCLUSIONS

PTCD is a newly described, very rare disorder with a variety of vision-threatening ocular manifestations. It is essential that the ophthalmologist be aware of the potential for neurotrophic cornea because timely treatment could prevent corneal scarring, perforation, and blindness.

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

Malformations involving the brainstem are very rare and present with a varied spectrum of clinical symptoms due to multiple cranial nerve palsies and pyramidal tract involvement. Of these, pontine tegmental cap dysplasia is a very unusual malformation, characterized by ventral pons hypoplasia and an ectopic dorsal band of tissue, projecting into the fourth ventricle, from dorsal pontine tegmentum. A 4-year-old male child, presenting with left facial nerve palsy, revealed hypoplastic ventral pons and an ectopic structure on magnetic resonance imaging (MRI). The ectopic structure was isointense to pons, arose from the left side of dorsal pontine tegmentum, at pontomedullary junction and protruded into the fourth ventricle, impinging upon the left seventh and eighth cranial nerves. Diffusion tensor imaging (DTI) depicted abnormal white matter tracts in ectopic tissue with absent transverse pontine fibres and abnormal middle and superior cerebellar peduncles. The typical MRI appearance, coupled with DTI, helped us reach an accurate diagnosis of pontine tegmental cap dysplasia, in a setting of neurological dysfunction.

Imaging of congenital cranial dysinnervation disorders: What radiologist wants to know?

We aim to review the imaging features of congenital cranial dysinnervation disorders. Characteristic imaging findings can define subtypes of these disorders through assessment of cranial nerves, extraocular muscles, orbital, and brain abnormalities. Duane retraction syndrome shows absent or hypoplasic 6th cranial nerve and preserved extraocular muscles (EOM). Mobius syndrome shows absent 7th and 6th cranial nerves, absence of facial colliculus, flattening of the dorsal aspect of the pons, hypoplasia of the pons and medulla, and flattening of the 4th ventricular floor. Congenital fibrosis of the extraocular muscles reveals unilateral or bilateral hypoplasia or aplasia of the 3rd cranial nerve, atrophy of superior rectus and levator palpebrae superioris muscles, and atrophy of the brainstem and cerebellar hemispheres. Horizontal gaze palsy and progressive scoliosis show characteristic split pons sign, butterfly medulla, absent facial colliculi, and spinal scoliosis. HOXA1 Mutations show a bilateral absence of 6th cranial nerves with the underdeveloped inner ear. Pontine Cap Tegmental Dysplasia shows ventral pontine hypoplasia, dorsal tegmental projection into the 4th ventricle, and variable cranial nerve deficits.

Case 266: Pontine Tegmental Cap Dysplasia

History A 1-year-old boy was referred for cochlear implant assessment after he received a diagnosis of bilateral profound sensorineural hearing loss at neonatal hearing screening shortly after birth. The child was born at term via uneventful delivery, and there was no history of familial hearing loss or maternal illness. Tympanic membranes were normal, and hearing loss was confirmed with auditory brainstem testing, which showed no response from either ear. Hearing aids were provided from 3 months of age, but no behavioral responses were noted when these were worn. He was also noted to have some mild developmental delay throughout his 1st year of life and was slow to crawl, roll over, and stand up. Physical examination showed no syndromic features or physical abnormalities. Ophthalmology confirmed normal vision and visual movements but bilateral anesthetic corneas. He had corneal abrasions due to minor repeated corneal trauma, and left-sided tarsorraphy was performed at 6 months. Facial nerve function, swallow, and voice quality were normal. To assess suitability for a cochlear implant, the patient underwent MRI of the temporal lobe and brain and thin-section CT of the temporal bones. The patient subsequently underwent left cochlear implantation.

Pontine tegmental cap dysplasia with a duplicated internal auditory canal

Pontine tegmental cap dysplasia (PTCD) is a rare neurological syndrome that results in a hypoplastic ventral pons, tegmental cap at the dorsal pons, and cranial nerve dysfunction. The most common symptoms are hearing loss and speech problems. We present a case of a 9-month-old male who presented with developmental delay and hypotonia. Magnetic resonance imaging revealed ectopic dorsal transverse pontine fibers and a cap-like protrusion of the dorsal pons. Diffusion tensor imaging showed that the ventral pontine fibers were absent. The cause of PTCD is undiscovered, but proposed hypotheses include dysfunction in axonal guidance, neuronal migration, and ciliary protein function. PTCD is a rare neurological disorder, but the diagnosis can be suggested with MRI using diffusion tensor imaging as an aid.

Duplicated Internal Auditory Canal: High-Resolution CT and MRI Findings

Objective

To summarize the high-resolution computed tomography (HRCT) and magnetic resonance imaging (HRMRI) features of duplicated internal auditory canals (DIACs).

Materials and Methods

Ear HRCT data of 64813 patients with sensorineural hearing loss (SNHL), obtained between August 2009 and November 2017, were reviewed. Among these patients, 12 (13 ears) were found to have DIACs, 9 of whom underwent HRMRI. Their images were evaluated by two otoradiologists.

Results

The rate of occurrence of DIAC among SNHL patients was 0.019% (12/64813). The internal auditory canals of 13 ears were divided into double canals by complete (n = 6) and incomplete (n = 7) bony septa, with varied orientations ranging from horizontal to approximately vertical. All of the anterosuperior canals extended into the facial nerve (FN) canal, except for 1, which also extended to the vestibule. The posteroinferior canals ended in the cochlea and vestibule, except for 2, which also connected to the FN canals. Magnetic resonance images revealed that 77.8% (7/9) and 22.2% (2/9) of vestibulocochlear nerves (VCNs) were aplastic and hypoplastic, respectively. Furthermore, 88.9% (8/9) of FNs were normal, except for 1, which was hypoplastic. All of the affected ears also had other ear anomalies: a narrow, bony cochlear nerve canal was the most common other anomaly, accounting for 92.3% (12/13). Malformations of other systems were not found.

Conclusion

Double-canal appearance is a characteristic finding of DIAC on HRCT, and it is usually accompanied by other ear anomalies. The VCN usually appears aplastic, with a normal FN, on HRMRI.

Fetal and neonatal neurogenetics

Disorders of the developing nervous system may be of genetic origin, comprising congenital malformations of spine and brain as well as metabolic or vascular disorders that affect normal brain development. Acquired causes include congenital infections, hypoxic-ischemic or traumatic brain injury, and a number of rare neoplasms. This chapter focuses on the clinical presentation and workup of neurogenetic disorders presenting in the fetal or neonatal period. After a summary of the most frequent clinical presentations, clues from history taking and clinical examination are illustrated with short case reports. This is followed by a discussion of the different tools available for the workup of neurogenetic disorders, including the various genetic techniques with their advantages and disadvantages. The implications of a molecular genetic diagnosis for the patient and family are addressed in the section on counseling. The chapter concludes with a proposed workflow that may help the clinician when confronted with a potential neurogenetic disorder in the fetal or neonatal period.