The foramen ovale "mirage" and how this impacts percutaneous cannulation for treatment of trigeminal neuralgia: a report of two cases.

Percutaneous stereotactic radiofrequency rhizotomy (PSR) for trigeminal neuralgia most commonly utilizes 2D fluoroscopy for intraoperative needle guidance into the foramen ovale (FO). We describe two cases in which needle advancement into FO was unachievable despite appropriate needle placement on biplane fluoroscopy. Intraoperative multiplanar reconstruction was helpful in more accurately depicting foraminal anatomy which allowed the manipulation of the tip of the needle, which was followed by successful FO cannulation. We propose that this "mirage" is likely created by the inherent nature of X-ray-based fluoroscopy in which the FO appears to be readily penetrable, when in fact the 3D anatomy actually prevents cannulation.

Time dependent pattern of cellular characteristics causing ventriculoperitoneal shunt failure in children.

BACKGROUND: Ventriculoperitoneal shunt obstruction remains a major problem in pediatric neurosurgery. We analyzed the tissue reaction to ventriculoperitoneal shunts and compared the histology versus time elapsed to shunt failure. METHODS: 85 ventricular catheter tissues samples obtained from 71 patients were reviewed along with time elapsed to shunt revision. Pathology reports of all tissue samples were divided into three categories: inflammatory based on the presence of lymphocytes, macrophages, and microglial cells; reactive based on the presence of fibro-connective tissue, reactive astrocytes, and Rosenthal fibers; and normal brain tissue based on presence of choroid plexus. These categories were then grouped according to time elapsed to shunt revision. Group I had those shunts revised <6 months, group II included shunts revised between 6 months and 3 years, while group III had shunts revised after more than 3 years. RESULTS: The incidence of inflammatory type of histology was 44% (16/36) in group I, 22% (6/27) in group II, and 18% (4/22) in group III. The reactive histology was 42% (15/36) in group I, 67% (18/27) in group II, and 77% (17/22) in group III. There was a clear noted difference of incidence between inflammatory versus reactive histology between early shunt failure compared to late shunt failure. Incidence of normal brain tissue remained high in group I with 8%, 11% in group II, and none in group III. CONCLUSION: Early shunt obstruction arises from pathologies different from those causing late shunt obstructions.

Suboccipital craniotomy in the surgical treatment of Chiari I malformation.

OBJECT: The object of this study was to present craniotomy for Chiari type I patients. MATERIALS AND METHODS: Six patients with Chiari type I underwent suboccipital craniotomy. All patients showed clinical improvement, and none had any complications. Two patients had syringomyelia; it disappeared in entirety. We describe the procedure for posterior fossa decompression. RESULTS: Three-dimensional volumetric analysis using Vitrea workstation for postoperative posterior fossa volumes was calculated and was seen to have been increased on an average, from pre-operative (168 cc) to postoperative volume (192 cc). CONCLUSION: We thus conclude that suboccipital craniotomy results in resolution of the Chiari symptoms yet achieves effective expansion of posterior fossa.

A case report of intraventricular gliofibroma.

Gliofibroma is a rare tumor with biphasic morphology. We report a case of a 3-month-old girl presenting with increasing head circumference. CT and MRI showed the presence of a large heterogeneous, nonenhancing tumor filling the atria and bodies of the lateral ventricles with caudal extension into the third ventricle. Hydrocephalus was noted. A biopsy was performed and pathology showed the presence of glial and collagenous tissue consistent with the diagnosis of gliofibroma. However, no mitosis or necrosis was seen. Immunohistochemistry was positive for glial fibrillary acid protein, Masson trichrome and reticulin. The patient was followed up for a period of 10 years. Recent MRI showed stable appearance of the tumor and clinically the patient is neurologically intact with normal cognitive development. Our case report has the longest follow-up so far reported in the literature, of 10 years. As evident from our case report, we recommend a conservative treatment approach for gliofibroma with benign histology.