Prepontine Space Research Articles

The prepontine block and its relevance for the development and treatment of hydrocephalus

ObjectivePulsatile CSF flow patterns include flow through the ventricles to the subarachnoid space and cisterns and from the infra- to the supratentorial subarachnoid space. In this study, we demonstrate how an obstruction at the level of the prepontine space may lead to obstructive hydrocephalus with specific radiological characteristics, as well as the implications for treatment options.MethodsWe retrospectively collected data of patients who underwent surgery between February 2010 and December 2022 for hydrocephalus secondary to a suspected prepontine block. One additional patient diagnosed with prepontine block who did not undergo surgery was also included. We excluded patients with a background of previous unrelated neurosurgical procedures or CNS infections.ResultsSix children and two adults were included. Three presented with hydrocephalus on imaging, without any other underlying pathology. Five had a suprasellar arachnoid cyst, with its lower border abating the pons and occluding the spinal subarachnoid space (SAS). All cases had an open aqueduct on T2 sagittal sequences, as well as an infracerebellar or retrocerebellar CSF collection. In most cases, a horizontal web was identified in the prepontine region. Seven cases were treated with an endoscopic fenestration. One patient subsequently underwent a shunt surgery. All the operated children reached normal developmental milestones after surgery.ConclusionsThis paper describes a rather small series of cases where clear obstruction was observed at the level of the prepontine subarachnoid space. We believe this anatomical subtlety adds to a better understanding of CSF pathways and the role of ETV in treating hydrocephalus, focusing on a small subgroup of patients without a clear obstruction.

Prepontine placement of an intrathecal baclofen pump catheter for treatment of dystonia

Background: Cerebral palsy with medically refractory spasticity and dystonia is a condition that often benefits from intrathecal baclofen pump therapy to treat these symptoms. In this case report, an intracranial baclofen catheter was placed in the prepontine space to improve withdrawal symptoms in a patient unable to undergo new lumbar catheter placement due to infection.Case Description: A 22-year-old female with past medical history of cerebral palsy presented with baclofen pump failure and was unable to undergo placement of a new lumbar baclofen catheter due to an infection in her lower back precluding safe and efficacious catheter placement. It was decided the patient would benefit from intrathecal baclofen administered in the prepontine space as a means to avoid a lumbar catheter and thus bypass this prior infection site. An endoscopic third ventriculostomy (ETV) was performed with the endoscope and the distal end of the baclofen pump catheter was fed through this ETV into the prepontine space. Placement in the prepontine space was confirmed by a follow-up head computed tomography. There was a significant improvement in autonomic symptoms and spasticity. By postoperative day 5, the patient was surgically and medically cleared for discharge.Conclusion: In cases of severe baclofen withdrawal due to dysfunctional pumps, immediate reversal is preferred but may not be feasible due to factors such as infection. This case report has demonstrated that prepontine catheter placement can be effective for the administration of baclofen to reverse withdrawal symptoms in these types of patients.

Surgical anatomy of a neurenteric cyst anterior to the brainstem

The authors report on a sixteen-month old boy who presented a neurenteric cyst located in the cervicomedullary junction, anterior to the brain stem. Centred on the ventral aspect of the premedullary cistern, the cyst extended from the prepontine space to the cervicomedullary junction, causing important brain stem compression. The lesion was totally removed via a posterior approach with suboccipital craniotomy and laminectomy of C1. After surgery the patient recovered his neurological function and the postoperative MRI showed total resection of the cyst.

Combined petrosal approach.

The combined petrosal approach to the lateral skull base merges a retrolabyrinthine-presigmoid posterior fossa craniotomy with an adjacent middle fossa craniotomy, which are rendered continuous by division of the tentorium. This is a hearing-preserving approach that affords wide access to the lateral aspect of the clivus, the prepontine space, and the cerebellopontine angle. This article details the historical development of the combined petrosal approach alongside a description. In particular, the critically relevant anatomy is reviewed, including the course of the vein of Labbé, with a view toward avoiding the known complications associated with this approach. Outcomes for application of this approach as applied for various lesions are also reviewed as portrayed by the current literature. The combined petrosal approach affords wide access to the lateral skull base in the middle and posterior fossa. The approach and the lesions addressed by this approach involve delicate and sensitive anatomy. We review the evolution of this approach and highlight advancements that have allowed the combined petrosal approach to be a safe addition to the surgeon's armamentarium.

Silent cerebral MRI findings in lupus nephritis patients: Is it clinically significant?

Lupus nephritis (LN) carries high morbidity and mortality and whenever added to neuropsychiatric manifestations lead to more unfavorable prognosis. Though silent brain MRI findings in systemic lupus erythematosus (SLE) had been widely studied, the current work focused on LN patients comparing them to those without kidney affection, studying their cerebral MRI and its correlation with the histopathological classes of LN and disease activity. This may enable us to know more about early brain affection in LN patients for better follow up, management, and prognosis of this serious comorbidity. Cerebral MRI and MRA were studied in 40 SLE patients without neuropsychiatric manifestations; 20 LN patients with different histopathological classes and 20 patients without kidney affection. Disease activity was assessed for all patients using SLE disease activity index (SLEDAI). Abnormal MRI brain findings were more common in LN patients “though non significant” (P = 0.9). The most common lesions were white matter hyperintense lesions (WMHLs). Number and size of such lesions were significantly higher in LN patients (1.8 fold that of non nephritis, P = 0.003 and 0.03, respectively) and positively correlated with urea, creatinine, urinary albumin/creatinine ratio, SLEDAI, ESR, CRP, and grades of renal biopsy and negatively correlated with C3 and C4. Cortical atrophy and prepontine space dilatation were also significantly higher in LN patients (P = 0.01). Asymptomatic MRI brain lesions whenever present in LN patients, they are usually clinically significant and well correlate to laboratory parameters of LN, grades of renal biopsy, and disease activity independent to age, sex and hypertension.

Endoscopic third ventriculostomy through lamina terminalis: A feasible alternative to standard endoscopic third ventriculostomy.

Endoscopic third ventriculostomy (ETV), wherein a stoma is created in the floor of the third ventricle, has now become the standard procedure for noncommunicating hydrocephalus across the world. However, in certain situations, this procedure may pose technical difficulties. These include a narrow prepontine space, vascularized third ventricular floor, the presence of prominent blood vessels traversing within the prepontine space, significant basal exudates, thickened and ill-defined third ventricular floor, and distorted floor anatomy. In such situations, an endoscopic lamina terminalis opening may provide a safer and more effective alternative to the standard technique. The paper aims to discuss the different indications, technical nuances, and outcome of endoscopic third ventriculostomy through the lamina terminalis (ETV LT) utilizing the standard transventricular transforaminal route. A total of 240 patients underwent ETV between January 2007 and January 2014. Of these patients, 8 patients required an EVT LT and these patients formed the subset of patients for the present study. In all the 8 patients, the decision to perform fenestration of the LT during the endoscopic procedure was taken intraoperatively. We qualified a procedure to be a success when a second procedure was not required subsequently. Of the eight patients in whom ETV LT was done, four had aqueductal stenosis (including one case of post-primary ETV), three patients were diagnosed with post-meningitic hydrocephalus, and the remaining patient had a posterior fossa tumor. The procedure was successful in 6 of our patients who did not require a second procedure till the last follow-up. Endoscopic transventricular transforaminal LT fenestration with a flexible neuroendoscope is a feasible alternative to the standard ETV when technical difficulties precludes safe performance of the latter procedure.

Endoscopic third ventriculostomy and choroid plexus cauterization with a rigid neuroendoscope in infants with hydrocephalus.

OBJECT Combining endoscopic third ventriculostomy (ETV) with choroid plexus cauterization (CPC) has been shown to improve the success rate compared with ETV alone in infants (less than 24 months) with hydrocephalus who were treated in developing countries. The authors sought to evaluate the safety and efficacy of this procedure, using a rigid neuroendoscope, in a single North American center, and to assess whether the ETV success score (ETVSS), the CURE Children's Hospital of Uganda ETVSS (CCHU ETVSS), and other pre- and intraoperative variables could predict success. METHODS The authors performed a retrospective review of consecutive ETV/CPC procedures performed using a rigid neuroendoscope to treat infantile hydrocephalus. The infants underwent the procedure at Miami Children's Hospital between January 2007 and 2014, with at least one postoperative follow-up. Duration of follow-up or time to failure of ETV/CPC, the primary outcome measure, was documented. A repeat CSF diversion procedure or death was considered as a failure of ETV/CPC. The time to event was measured using a Kaplan-Meier analysis. The authors analyzed ETVSS, CCHU ETVSS, and pre- and intraoperative variables to determine their suitability to predict success. RESULTS Eighty-five patients (45 boys) with a mean age of 4.3 months (range 1 day to 20 months) underwent ETV/CPC. Etiology included intraventricular hemorrhage of prematurity in 44 patients (51.7%), myelomeningocele (MMC) in 7 (8.2%), congenital aqueductal stenosis in 12 (14.1%), congenital communicating hydrocephalus in 6 (7.1%), Dandy-Walker complex in 6 (7.1%), postinfectious hydrocephalus in 5 (5.8%), and other cause in 5 (5.8%). Six procedure-related complications occurred in 5 (5.8%) patients, including 2 hygromas, 1 CSF leak, and 3 infections. There were 3 mortalities in this cohort. ETV/CPC was successful in 42.1%, 37.7%, and 36.8% of patients at 6, 12, and 24 months follow-up, respectively. The median (95% CI) time to ETV/CPC failure was 4.0 months (0.9-7.1 months). In univariate analyses, both the ETVSS (hazard ratio [HR] 1.03; 95% CI 1.01-1.05; p = 0.004) and CCHU ETVSS (HR 1.48; 95% CI 1.04-2.09; p = .028) were predictive of outcome following ETV/CPC. In multivariate analysis, the presence of prepontine scarring was associated with ETV/CPC failure (HR 0.34; 95% CI 0.19-0.63; p < 0.001). Other variables, such as radiological criteria (prepontine interval, prepontine space, aqueductal stenosis, Third Ventricular Morphology Index) and intraoperative findings (ventriculostomy pulsations, extent of CPC), did not predict outcome. CONCLUSIONS ETV/CPC is a feasible alternative to ETV and ventriculoperitoneal shunt in infants with hydrocephalus. Both the ETVSS and CCHU ETVSS predicted success following ETV/CPC in this single-center North American cohort of patients.

Endoscopic Third Ventriculostomy: Preoperative Considerations and Intraoperative Strategy Based on 300 Procedures

Although successful endoscopic third ventriculostomy (ETV) has been reported for many indications, peculiarities of the surgical technique in each separate indication require particular respect. A detailed account of the authors' surgical technique, their presurgical considerations, and their intraoperative strategies to perform ETV is presented. Surgery of representative obstructive hydrocephalus cases in posterior fossa lesions (cerebellar infarction, posterior fossa tumor), in distortion of the ventricular system (intracranial hemorrhage, basilar artery aneurysm) and in membranous obstruction (aqueductal stenosis, posterior fossa malformation), is illustrated in detail. In posterior fossa lesions, careful evaluation of the prepontine space and localization of the basilar artery is mandatory. Recognition of mammillary bodies and infundibular recess is of particular importance since the third ventricle floor is rather thick and nontranslucent. In distortion of the ventricular system, careful analysis of the preoperative imaging allows the selection of the optimal approach. Sometimes, blood clot removal and vigorous irrigation is required. Frequently, the landmarks are difficult to identify. These are cases for experienced endoscopic neurosurgeons. In aqueductal stenosis and posterior fossa malformation, perforation of the often thin and translucent ventricular floor is easy because of clear anatomical landmarks. Those are ideal candidates for ETV. For experienced neuroendoscopists, the authors advocate inspection of the fourth ventricle with a flexible scope to ensure cerebrospinal fluid (CSF) circulation obstruction. ETV is a frequent and well-established endoscopic technique. Based on the underlying pathology, the technique has to be modified to obtain good results with minimal complications.

Endoscopic third ventriculostomy in adults: a technique for dealing with the neural (opaque) floor

An opaque (neural) floor of the third ventricle is considered an obstacle to safe penetration of the floor of the third ventricle in endoscopic third ventriculostomy (ETV). The direct technique of endoscopic coring ("cookie cut") of the opaque (neural) floor of the third ventricle is described in 41 cases among a total of 101 consecutive adult ETVs. A 0° endoscope in a 4.6-mm irrigating sheath was used to press and core ("cookie cut") a section of the tuber cinereum, thereby exposing the underlying membranes and vasculature. Thereafter, the endoscopic apparatus was used to penetrate the membrane into the prepontine space. Among 101 consecutive ETVs performed in adults, there were 41 instances of an opaque floor in which the coring technique was used. The basilar artery (BA) complex was in the intended path of penetration in 13 cases. There were no perioperative deaths or vascular injuries. No cases were aborted because of the opaque floor or the configuration of the BA complex. The clinical success rate in the opaque floor group was 80% (33 of 41 patients). An opaque (neural) floor is frequently seen in adults during ETV. Removing the floor by the core ("cookie cut") method is a safe means of revealing the underlying BA complex and membranous structures prior to penetration into the prepontine cistern. On occasion, the BA complex may be in the path of penetration, and one can maneuver the endoscope to displace the vasculature to successfully accomplish the ETV.

Sudden death due to subarachnoid bleeding from ecchordosis physaliphora

Ecchordosis physaliphora (EP) is a rare intracranial mass derived from ectopic notochordal tissue. It is usually a fortuitous finding at autopsy or by computed tomography/magnetic resonance imaging. Very few authors have described an EP-associated symptomatology. In this study, we report a case of the sudden and unexpected death of a 48-year-old woman. At autopsy, the cause of death was subarachnoid bleeding, the origin of which was identified as a gelatinous mass stemming from the dura mater and occupying the prepontine space. Further histological and immunohistochemical investigations allowed the diagnosis of EP.

Functional analysis of third ventriculostomy patency with phase-contrast MRI velocity measurements.

Our purpose was to explore the utility of cine phase-contrast MRI velocity measurements in determining the functional status of third ventriculostomies, and to correlate the quantitative velocity data with clinical follow-up. We examined six patients with third ventriculostomies and 12 normal subjects by phase-contrast MRI. The maximum craniocaudal to maximum caudocranial velocity range was measured at regions of interest near the third ventricular floor, and in cerebrospinal fluid anterior to the upper pons and spinal cord on midline sagittal images. Ratios of the velocities of both the third ventricle and prepontine space to the space anterior to the spinal cord were obtained. The velocities near the third ventricular floor and in the pontine cistern were significantly higher in patients than in normal subjects, but the velocity anterior to the spinal cord was similar between the groups. The velocity ratios, used to normalize individual differences, were also higher in patients than in controls. Two patients had lower velocity ratios than their fellows at the third ventricular floor and in the pontine cistern; one required a shunt 11 months later, while in the other, who had a third ventricular/thalamic tumor, the lower values probably reflect distortion of the third ventricular floor. We conclude that phase-contrast MR velocity measurements, specifically the velocity ratio between the high pontine cistern and the space anterior to the spinal cord, can help determine the functional status of third ventriculostomies.

MRI of trigeminal neuralgia: Initial clinical results in patients with vascular compression of the trigeminal nerve

The most common cause of the idiopathic trigeminal neuralgia are tortuous arteries in the prepontine space. The trigeminal nerve can be compressed by the superior cerebellar artery, the inferior cerebellar artery, or the basilar artery. Seldom the nerve is traumatised by an enlarged vein. Because an operative decompression of the nerve can relieve pain, a preoperative evaluation is needed. Angiography of the vertebral arteries is able to predict a tortuous artery close to the trigeminal nerve but cannot show the nerve itself. MRI can show tortuous vessels and the trigeminal nerve together on one single image by means of a 3D gradient-echo FLASH sequence with an effective slice thickness of approximately 1 mm and secondary reconstructions in every desired plane. MRI thus provides an efficient tool for the evaluation of patients with trigeminal neuralgia.