Andrew J.J. Law

Ventricular catheter placement accuracy in non-stereotactic shunt surgery for hydrocephalus

We aimed to compare the accuracy of different shunt catheter approaches to the lateral ventricle in adults with hydrocephalus. We conducted a retrospective review of 138 consecutive patients with hydrocephalus undergoing freehand initial shunt surgery. Of these, 79 had a post-operative brain scan and therefore the results were available for analysis. Scans were graded for successful catheter tip placement in the ventricular target zones: the frontal horn for frontal and occipital approaches, and the atrium for the parietal approach. Ventricular target zones were successfully catheterized in 85% of parietal and 64% of frontal shunts (this difference is not statistically significant). In contrast, only 42% of occipital shunts were correctly placed (p<0.01). Therefore, parietal and frontal catheters are more likely to be placed successfully in the target ventricle. This may be due to the smaller range of successful trajectories open to the occipital approach. Solutions to this problem may include using the theoretically favourable frontal approach for freehand surgery or using stereotactic guidance.

Cortical ependymoma or monomorphous angiocentric glioma

Ependymoma is the third most common childhood intracranial tumor after medulloblastoma and pilocytic astrocytoma. Most ependymomas occur in the posterior fossa and spinal cord but only five cases confined to the cerebral cortex have been reported. The current case is a 5‐year‐old boy with a somewhat ill‐defined cortical tumor diagnosed as pilocytic astrocytoma on biopsy, and treated with radiotherapy. Nine years later, resection of the essentially unaltered tumor was performed for treatment of intractable seizures. Histologically, the tumor had some areas with the typical appearance of ependymoma as well other areas which contained piloid cells. There was also evidence of focal infiltrative growth. These findings bore resemblance to a recently described entity monomorphous angiocentric glioma/angiocentric neuroepithelial tumor, which combines features of ependymoma with pilocytic and diffuse astrocytomas. Both cortical ependymomas and angiocentric monomorphous glioma/angiocentric neuroepithelial tumor appear to be low‐grade tumors although their rarity makes accurate prognosis problematic. The current case has features of both entities, suggesting they may be closely related.

Ventricular catheter trajectories from traditional shunt approaches: a morphometric study in adults with hydrocephalus

OBJECTnThe purpose of this study was to compare the margins of error of different shunt catheter approaches to the lateral ventricle and assess surface anatomical aiming landmarks for free-hand ventricular catheter insertion in adult patients with hydrocephalus.nnnMETHODSnFour adults who had undergone stereotactic brain magnetic resonance (MR) imaging and had normal ventricles, and 7 prospectively recruited adult patients with acute hydrocephalus were selected for inclusion in this study. Reconstructed MR images obtained prior to surgical intervention were geometrically analyzed with regard to frontal, parietal, and parietooccipital (occipital) approaches in both hemispheres.nnnRESULTSnThe ventricular target zones were as follows: the frontal horn for frontal and occipital approaches, and the atrium/posterior horn for parietal approaches. The range of possible angles for successful catheter insertion was smallest for the occipital approach (8 degrees in the sagittal plane and 11 degrees in the coronal plane), greater for parietal catheters (23 and 36 degrees ), and greatest for the frontal approach in models of hydrocephalic brains (42 and 30 degrees; p < 0.001 for all comparisons except frontal vs parietal, which did not reach statistical significance). There was no single landmark for aiming occipital or parietal catheters that achieved ventricular target cannulation in every case. Success was achieved in only 86% of procedures using occipital trajectories and in 66% of those using parietal trajectories.nnnCONCLUSIONSnThe occipital approach to ventricular catheter insertion provides the narrowest margin of error with regard to trajectory but has less aiming point variability than the parietal approach. The use of patient-specific stereotaxy rather than generic guides is required for totally reliable, first-pass ventricular catheterization via a posterior approach to shunt placement surgery in adults.

A survey of surgical techniques for catheterising the cerebral lateral ventricles.

The objective of this paper is to characterise the frequency of different surgical techniques for targeting the lateral ventricle in shunt surgery and the attitudes of Australasian neurosurgeons and advanced neurosurgical trainees to stereotactic adjuncts. Secondarily, we aim to learn from and collate the practical experiences of neurosurgeons for those attempting to improve their operative success. A survey of all practising and training members of the Neurosurgical Society of Australasia (NSA) was conducted. One hundred and eleven surveys were completed generating an overall response rate of 57%. Of those 108 performing shunt surgery, 10 (9%) preferred a frontal approach and 70 (65%) a posterior approach to the frontal horn. Twenty-seven neurosurgeons (25%) preferred the posterior approach to the atrium or body of the lateral ventricle. A wide range of burr hole sites and targeting landmarks were described and are discussed. There was no consistent pattern for neurosurgeons changing their preferred approach during their careers. Seventy-five per cent of respondents make adjustments to measurements for children by a wide range of methods. Frameless or frame-based stereotaxy is used at times by about half of all neurosurgeons. Posterior approaches to the lateral ventricle using freehand techniques are preferred among NSA members and their trainees but there are a wide variety of landmarks used. Many of these techniques have been developed over years of operative experience and could be modelled with planning software to assess their theoretical merits. There is no evidence of the uptake of generic accuracy guides but there is evidence of significant exposure to frameless stereotactic techniques that may grow in popularity as the technology improves.

Primary glioblastomas and anaplastic astrocytoma in a glioma family

A 72-year-old man presented with a short duration of symptoms relating to a right fronto-parietal glioblastoma and a family history of children with brain tumours. Analysis of the patients family tree revealed that out of seven children, he had a living son with anaplastic astrocytoma, a daughter who had died with a glioblastoma, and a son who had died with a histologically undiagnosed intrinsic brain tumour. One niece was also thought to have died from a brain tumour. All of the other affected family members had onset in their third or fourth decades. Tissue was only available from two of the affected individuals, precluding familial genetic analysis at this stage. There is no clinical evidence to support a diagnosis of a multiple cancer or neurocutaneous syndrome in this family. In view of what is known about the genetics of familial glioma, it is interesting to note the clinical evidence of both primary glioblastoma and anaplastic astrocytoma in the same kindred.

Acute hydrocephalus secondary to herpes simplex type II meningitis

A 34-year-old woman presented with a rapid onset of meningitic symptoms. Cerebrospinal fluid (CSF) from a lumbar puncture revealed a leucocytosis with a preponderance of monocytes, elevated protein and reduced glucose. Herpes simplex virus (HSV) type II was subsequently confirmed by polymerase chain reaction (PCR) of CSF. The patients level of consciousness deteriorated and a CT scan revealed hydrocephalus. The patient required placement of an external ventricular drain for 5 days; however, she made a full recovery without specific antiviral therapy. This is the first reported case of hydrocephalus secondary to isolated HSV type II meningitis.

Lumbar disc herniation exacerbating venous hypertension from a spinal perimedullary arteriovenous fistula of the filum terminale

Arteriovenous fistulas of the filum terminale are exceptionally rare spinal vascular malformations [1]. These lesions typically manifest with myelopathy due to spinal cord venous congestion and secondary ischemia. We describe a novel case of a filum terminale arteriovenous fistula (FTAVF) resulting in perimedullary venous hypertension which was exacerbated by a lumbar disc herniation. A 43 year-old male presented with two years of intermittent back pain and right-sided leg pain in an L5 dermatomal distribution. On neurological examination, the patient was full strength with normal reflexes. Thoracolumbar magnetic resonance imaging (MRI) showed a large, paracentral disc herniation at L4–5, resulting in significant central canal and bilateral neuroforaminal stenosis (Fig. 1A–B). Additionally, dilated pial vessels were noted over the surface of the conus medullaris. MR angiography (MRA) showed arterialization of flow within a prominent intrathecal lumbar vessel (Fig. 1C). Further evaluation with computed tomography angiography (CTA) showed abnormal pial vasculature opacifying during the arterial phase and extending from approximately T10 to L4–5. Based on the MRI/MRA and CTA findings, spinal angiography was performed to evaluate for a vascular malformation and characterize its angioarchitecture. Catheter angiography identified a FTAVF supplied by a perimedullary branch of the left L1 radicular artery, which contributed to the anterior spinal artery and, below the conus medullaris, the artery of the filum terminale (Fig. 1D). The FTAVF drained into the vein of the filum terminale, with a point of fistulization at the level of the L3 vertebral body. Along its descending course, the vein of the filum terminale was significantly compressed by the L4–5 disc herniation, resulting in ascending venous reflux into the anterior spinal vein. Thus, the venoushypertensiondue to the FTAVFwas exacerbated by obstruction of the draining vein by the herniated disc. The patient underwent L4–5 laminectomies, a left L4–5 discectomy, and ligation of the FTAVF with division of the filum terminale (Fig. 1E– F). Postoperative spinal angiography showed complete obliteration of the FTAVF, without evidence of early venous shunting (Fig. 1G). The