How I do it: Subtemporal transtentorial approach for cavernous malformation of the pons.

BACKGROUND: Removal of a pontine cavernous malformation requires sufficient exposure since any restriction on surgical freedom may lead to suboptimal visualization of the lesion, injury to the brainstem, and neurological catastrophe. METHODS: We describe and demonstrate the subtemporal transtentorial approach to a cavernous malformation of the upper pons, with emphasis on adequate surgical exposure while avoiding the need for extensive bone removal of the skull base. CONCLUSIONS: The meticulous technique is paramount to the successful removal of any brainstem cavernous malformation. Along with the surgical exposure, delicate handling of the malformation is demonstrated in the accompanying operative video.

Significance of the Cerebellopontine Cistern Cross-Sectional Area and Trigeminal Nerve Anatomy in Trigeminal Neuralgia: An Anatomical Study Using Magnetic Resonance Imaging.

AIM: To evaluate the relationship between trigeminal neuralgia (TN) and potential magnetic resonance imaging (MRI)-related measurements in patients with TN. MATERIAL AND METHODS: Retrospective analysis of 104 patients with TN was performed. MRI studies of 98 healthy controls were included in the study to compare the parameters with TN patients’ measurements. MRI measurements of cerebellopontine cistern (CPC) cross-sectional area, trigeminal-pontine angle (TPA) width, and trigeminal nerve cisternal segment length and thickness were assessed on both symptomatic and asymptomatic sides using 1.5T MRI with constructive interference in steady-state sequences. The images were interpreted by two radiologists blinded to the affected sides of the patients. RESULTS: There were significant differences between the symptomatic and asymptomatic sides in terms of mean trigeminal nerve length (8.8 ± 2.34 mm vs. 9.39 ± 2.29 mm; respectively, p=0.001) and thickness (20.9 ± 9.6 mm2 vs. 25 ± 9.98 mm2, respectively; p < 0.001). The median cerebellopontine cistern cross-sectional area was considerably lower on the symptomatic side compared with the asymptomatic side [201 mm2 (interquartile range=93) vs. 224.5 mm2 (interquartile range=77), respectively; p < 0.001]. There were no significant differences between the trigeminal-pontine angle width on either side (38.32 ± 10.38 vs. 38.78 ± 10.9, respectively; p=0.679). There were no statistically significant differences between the right and left sides regarding these parameters in the control group. CONCLUSION: Smaller CPC cross-sectional area, trigeminal nerve length, and trigeminal nerve thickness on MRI were demonstrated to commonly exist on the symptomatic side in patients with TN. We suggest that this narrow space may increase the risk of vascular compression on the nerve.

Is Asymmetry of the Pons Associated with Hand Function and Manual Ability after Arterial Ischemic Stroke in Children?

AIM: This study was designed to investigate how the asymmetry of the brain stem is related to hand function and manual ability after arterial ischemic stroke (AIS) diagnosed during childhood. METHOD: Patients diagnosed with AIS during childhood (> 5 years old, diagnosis > 2 years before recruitment) and typically developing peers were recruited by the Swiss Neuropediatric Stroke Registry. Brainstem cross-sectional areas of each side at the level of the pons were measured. Pinch and grip strength were measured with a dynamometer, quality of upper limb movement by the Melbourne Assessment 2 and manual ability by the ABILHAND-kids. An asymmetry index was calculated for all measures (except the ABILHAND-kids). Differences between groups and correlations were calculated using nonparametric statistics. RESULTS: Fourteen AIS survivors without hemiparesis, 10 AIS survivors with hemiparesis, and 47 typically developing peers were assessed. Patients with hemiparesis showed the highest brainstem asymmetry. There was a significant positive correlation between brainstem asymmetry, the asymmetry of strength and quality of upper limb movement, and a significant negative correlation between brainstem asymmetry and manual ability. INTERPRETATION: In pediatric AIS survivors, brainstem asymmetry can serve as an indirect measure of corticospinal tract integrity. It is significantly correlated with strength, quality of movement, and manual ability.

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. KEY POINTS: • Brainstem malformations affect 93% patients with mutated tubulin genes • MRI shows homolateral and crossed brainstem asymmetries, clefts and pons hypoplasia • DTI demonstrates irregular representation of transverse pontine fibres and fusion of corticospinal tracts.

Isolated neonatal bilateral vocal cord paralysis revealing a unilateral medullary defect: a case report.

BACKGROUND: Congenital bilateral vocal cord paralysis is a rare occurrence. Approximately half the cases are associated with a major comorbidity, usually neurological, neuromuscular or malformative. CASE PRESENTATION: In a male newborn, respiratory distress syndrome and stridor were observed immediately following birth. The cause was bilateral vocal cord paralysis in the adducted position. Neuroradiological investigation revealed a unilateral discontinuity between the upper pons and the right medulla oblongata. Hypoplasia of the right posterior hemiarches of C1-C2 and the right exo-occipital bone was observed, as was a small clivus. MR angiography showed the absence of the distal right vertebral artery, with hypoplasia and parietal irregularities of the proximal segments. Respiratory autonomy was not obtained despite endoscopic laser cordotomy, corticosteroid therapy and nasal continuous positive airway pressure. The infant died at the age of 4 weeks after treatment was limited to comfort care. CONCLUSIONS: A medullary lesion is an exceptional cause of congenital bilateral vocal cord paralysis. The strictly unilateral neurological and vascular defect and the absence of associated intracranial or extracranial malformation make this clinical case unique and suggest a disruptive mechanism. This case also highlights the help provided by advanced neuroimaging techniques, i.e. fibre tracking using diffusion tensor imaging, in the decision-making process.

A de novo missense mutation in the inositol 1,4,5-triphosphate receptor type 1 gene causing severe pontine and cerebellar hypoplasia: Expanding the phenotype of ITPR1-related spinocerebellar ataxia's.

We report a de novo missense mutation (c.7649T>A) in the inositol, 1,4,5 triphosphate receptor type 1 (ITPR1) gene in a patient with severe pontocerebellar hypoplasia. The mutation results in an amino acid substitution of a highly conserved isoleucine by asparagine (p. I2550N) in the transmembrane domain. Mutations and deletions of the ITPR1 gene are associated with several types of autosomal dominant spinocerebellar ataxia, varying in age of onset and severity. Patients have signs of cerebellar ataxia and at most, a mild cerebellar atrophy on MRI. In contrast, the patient we report here has profound cerebellar and pontine hypoplasia. Our finding therefore further expands the spectrum of ITPR1-related ataxias. © 2016 Wiley Periodicals, Inc.

A rare case of cerebellar agenesis: a probabilistic Constrained Spherical Deconvolution tractographic study.

Aim of this study is to show the potential of probabilistic tractographic techniques, based on the Constrained Spherical Deconvolution (CSD) algorithms, in recognizing white matter fiber bundle anomalies in patients with complex cerebral malformations, such as cerebellar agenesis. The morphological and tractographic study of a 17-year-old male patient affected by cerebellar agenesis was performed by using a 3Tesla MRI scanner. Genetic and neuropsychological tests were carried out. An MRI morphological study showed the absence of both cerebellar hemispheres and the flattening of the anterior side of the pons. Moreover, it showed a severe vermian hypoplasia with a minimal vermian residual. The study recognized two thin cerebellar remnants, medially in contact with the small vermian residual, at the pontine level. The third ventricle, morphologically normal, communicated with a permagna cerebello-medullary cistern. Probabilistic CSD tractography identified some abnormal and aberrant infratentorial tracts, symmetrical on both sides. In particular, the transverse pontine fibers were absent and the following tracts with aberrant trajectories have been identified: "cerebello-thalamic" tracts; "fronto-cerebellar" tracts; and ipsilateral and contralateral "spino-cerebellar" tracts. Abnormal tracts connecting the two thin cerebellar remnants have also been detected. There were no visible alterations in the main supratentorial tracts in either side. Neuropsychiatric evaluation showed moderate cognitive-motor impairment with discrete adaptive compensation. Probabilistic CSD tractography is a promising technique that overcome reconstruction biases of other diffusion tensor-based approaches and allowed us to recognize, in a patient with cerebellar agenesis, abnormal tracts and aberrant trajectories of normally existing tracts.

Generation and characterization of mice harboring a conditional CXCL12 allele.

The chemokine CXCL12 has important functions in immune and central nervous systems. Moreover, a global disruption of CXCL12 in mice results in perinatal lethality. To circumvent this impediment and provide a tool for analyzing CXCL12 functions in specific organ systems, we have generated a mouse line harboring a loxP-site flanked exon 2 of CXCL12. A germ line deleter, ß-actin::cre was used to remove a CXCL12 exon 2 and subsequently systemic CXCL12 exon 2 deficient embryos were generated. These mutant embryos showed a marked depletion of CXCL12 transcript. As expected from the global mutant phenotype, our mutants were also characterized by highly irregular cerebellar cytoarchitecture of the external granule layer as well as altered radial migration of midbrain dopaminergic neurons. Importantly, migration of the pontine grey nucleus (PGN) was derailed and remarkably resembled the global mutant phenotype of the CXCL12 receptor - CXCR4 in this system. Despite the fact that CXCL12 signaling can be mediated through receptors other than CXCR4, our results indicate a monogamous relationship between the CXCL12 ligand and CXCR4 receptor in controlling PGN migration. Our findings further expand on the understanding of CXCL12 function in PGN development. Moreover, phenotypic similarities between our mutants and mice harboring a global CXCL12 disruption support the validity of our line. Importantly, these results strongly suggest that our conditional CXCL12 line can be used as a powerful tool to manipulate CXCL12 signaling and function in vivo.

Endoscopic endonasal transclival approach to a pontine cavernous malformation: case report.

Cavernous malformations of the brainstem are difficult to manage because of their location in eloquent tissue and their high propensity for symptomatic bleeding. Traditional neurosurgical approaches are often associated with significant morbidities. Here we present the case of a 15 year-old male patient with an acute onset of severe cephalalgia associated with neurological signs (right cranial nerve VI, VII and VIII palsies). MRI revealed a ventral pontine cavernous malformation with signs of recent bleeding. The lesion was removed by way of an endoscopic endonasal transclival approach. Post-operative neurological examination showed a dramatic improvement in cranial nerves function. The patient remains stable two years after surgery.

T1 Hyperintense Prepontine Mass with Restricted Diffusion--A White Epidermoid or a Neuroenteric Cyst?

Neuroenteric cysts (NC) are benign, congenital malformation which are of endodermal origin commonly located in the central nervous system. We report a case of intracranial NC with squamous metaplasia and xanthogranulomatous response masquerading as a white epidermoid on conventional MRI sequences. Lesion showed two components on T2W-images. We observed differential diffusion characteristics including fractional anisotropy, radial diffusivity and axial diffusivity within the two components of the lesion.

Pontine tegmental cap dysplasia: report of two new cases from Kuwait.

We describe two patients (a Filipino boy aged 2.7 years and a Kuwaiti girl aged 4.8 Years) with clinical and MRI findings consistent with the diagnosis of pontine tegmental cap dysplasia (PTCD) and compare them with 23 other cases reported in the literature. Both presented with feeding problems (VII nerve), sensori-neural deafness (VIII nerve) and hypotonia from birth and later developed corneal opacities due to loss of corneal sensation (V nerve). They have severe psychomotor developmental delay. The MRI of their brain showed a flattened ventral pons, vaulted "cap"- like structure protruding into 4th ventricle and a "molar tooth" sign. One of our patients also had Tetralogy of Fallot (TOF) successfully corrected. The other had no extracranial manifestations. The findings in our patients are similar to those reported except for the occurrence of TOF which has not been reported before in association with PTCD.

Decision-making in classic trigeminal neuralgia concurrent with a pontine cavernous malformation: Causal or coincidental association?

Trigeminal neuralgia is classically associated with neurovascular compression of the trigeminal nerve, at the root entry zone (REZ). However, patients are occasionally affected by intra-axial involvement of trigeminal sensory fibers caused by demyelinating diseases, strokes and, rarely, pontine cavernous malformations. We discuss the management strategies and decision-making process in a 55-year-old patient, affected by trigeminal neuralgia with 2 potential causative mechanisms: a neurovascular conflict at the trigeminal REZ and an ipsilateral cavernous malformation at the pontine nucleus of the trigeminal nerve.

Pontine malformation, undecussated pyramidal tracts, and regional polymicrogyria: a new syndrome.

BACKGROUND: Horizontal gaze palsy and progressive scoliosis is caused by mutations in the ROBO3 gene, which plays a role in axonal guidance during brain development. Horizontal gaze palsy and progressive scoliosis is characterized by the congenital absence of conjugate lateral eye movements with preserved vertical gaze and progressive scoliosis as well as dysgenesis of brainstem structures and ipsilateral projection of the pyramidal tract. PATIENT: A 4-year, 11-month, girl presented with psychomotor retardation and autistic traits. Magnetic resonance imaging revealed hypoplasia and malformation of the ventral portion of the pons and medulla oblongata. Diffusion tensor imaging revealed the absence of decussation of the bilateral pyramidal tracts. These findings were similar to the typical findings for horizontal gaze palsy and progressive scoliosis. However, restriction of horizontal eye movement was minimal, and bilateral polymicrogyria were also noted in the occipitotemporal cortex in the present patient. These findings have not been previously reported in patients with horizontal gaze palsy and progressive scoliosis. No mutations in the ROBO3, SLIT1, SLIT2, NTN1, SEMA3 A, or SEMA3 F genes were identified. CONCLUSION: This child may have a disorder caused by an unidentified factor, other than a mutation in the genes analyzed, involved in corticogenesis, axonal guidance, and brainstem morphogenesis.

Subdural effusions and lack of early pontocerebellar hypoplasia in siblings with RARS2 mutations.

Mutations in the recently described RARS2 gene encoding for mitochondrial arginyl-transfer RNA synthetase give rise to a disorder characterised by early onset seizures, progressive microcephaly and developmental delay. The disorder was named pontocerebellar hypoplasia type 6 (PCH6) based on the corresponding radiological findings observed in the original cases. We report two siblings with the RARS2 mutation who displayed typical clinical features of PCH6, but who had distinct neuroimaging features. Early scans showed marked supratentorial, rather than infratentorial, atrophy, and the pons remained preserved throughout. One sibling also had bilateral subdural effusions at presentation. The deceleration in head growth pointed to an evolving genetic/metabolic process giving rise to cerebral atrophy and secondary subdural effusions. RARS2 mutations should be considered in infants presenting with seizures, subdural effusions, decelerating head growth and evidence of cerebral atrophy even in the absence of pontocerebellar hypoplasia on imaging.

Two different manifestations of locked-in syndrome.

Locked-in syndrome (LIS) is an entity that usually occur a consequence of the lesion of ventral part of pons. Etiology of locked-in syndrome can be vascular and nonvascular origin. Locked-in syndrome usually occurs as a consequence of thrombosis of intermedial segment of basilar artery that induces bilateral infarction of the ventrobasal part of the pons. Additionally, LIS can be caused by trauma which often leads to posttraumatic thrombosis of basilar artery. The incidence of locked-in syndrome is still unknown. The basic clinical features of locked-in syndrome are: quadriplegia (a consequence of disruption of corticospinal pathways located in ventral part of pons), different stages of paralysis of mimic musculature, paralysis of pharynx, tongue and palate with mutism and anarthria. The patient can not move, but is conscious and can communicate only by eye movements. Two patients with locked-in syndrome were present in this article. In the first case, the patient had classic locked-in syndrome that was first described by Plum and Posner. Other patient had incomplete form of locket-in syndrome which was first described by Bauer. In these two patients locked-in syndrome occurred as a consequence of trauma. In the first patient locked-in syndrome was caused by direct contusion of ventral part of pons while in other patient locked-in syndrome was a consequence of posttraumatic thrombosis of vertebrobasilar artery. The introduction of anticoagulant therapy, besides the other measures of intensive therapy, has shown complete justification in the second patient. The gradual partial recovery of neurologic deficit has developed in the second patient without any additional complications.

Pontocerebellar hypoplasia in extreme prematurity: clinical and neuroimaging findings.

The involvement of the cerebellum in unfavorable outcomes of extreme prematurity is increasingly recognized. Evidence implicates both cerebellar injury and cerebellar growth failure, which, along with supratentorial lesions, aggravate motor and developmental outcomes. We describe clinical and neuroradiologic findings of 12 extremely premature patients with acquired pontocerebellar hypoplasia (mean follow-up, 4 years). Patients' neuromotor outcomes involved combined motor abnormalities (spasticity, dystonia, and ataxia), whereas 25% were ambulatory by age 4 years. All patients exhibited developmental delays of variable degrees. One patient died at age 7.5 years. The possible etiopathogenesis, presentations, sequelae, and differential diagnoses of acquired pontocerebellar hypoplasia are discussed.