Tentorial Venous Anatomy: Variation in the Healthy Population

BACKGROUND AND PURPOSE

A new transtentorial venous system consisting of medial, intermediate, and lateral tentorial veins, connecting infra- and supratentorial compartments, was recently shown in 2 cadaver dissections and 2 patient scans. We sought to characterize the venous patterns within the tentorium and their relation to measures of skull development in a cohort of healthy adults.

MATERIALS AND METHODS

We retrospectively reviewed tentorial venous anatomy of the head using CTA/CTV performed for routine care or research purposes in 238 patients. Included studies had adequate contrast opacification of venous structures and a section thickness of ≤2 mm; we excluded cases with space-occupying lesions and vascular pathologies. Tentorial angle, dural sinus configurations, and measures of skull base development were assessed as predictors of tentorial venous anatomy variation via Cramér V association, the binary encoded Pearson correlation, and nearest-point algorithm with the Euclidean distance metric for clustering.

RESULTS

Tentorial vein development was related to the ringed configuration of the tentorial sinuses (P < .005). There were 3 configurations. Groups 1A and 1B (n = 50/238) had ringed configuration, while group 2 did not (n = 188/238). Group 1A (n = 38/50) had a medialized ringed configuration, and group 1B had a lateralized ringed configuration (n = 12/50). Measurements of skull base development were predictive of these groups. The ringed configuration of group 1 was related to the presence of a split confluens, which correlated with a decreased internal auditory canal-petroclival fissure angle. Configuration 1A was related to the degree of petrous apex pneumatization (P value = .010).

CONCLUSIONS

Variations in the transtentorial venous system directly correlate with cranial development.

Peripheral and central hypomyelination with hypogonadotropic hypogonadism and hypodontia

We identified four unrelated patients (three female, one male) aged 20 to 30 years with hypomyelination, pituitary hypogonadotropic hypogonadism, and hypodontia. Electron microscopy and myelin protein immunohistochemistry of sural nerves showed granular debris-lined clefts, expanded abaxonal space, outpocketing with vacuolar disruption, and loss of normal myelin periodicity. Reduced galactocerebroside, sphingomyelin, and GM1-N-acetylglucosamine and increased esterified cholesterol were found. This is a clinically homogeneous progressive hypomyelinating disorder. The term 4H syndrome is suggested.

Clinical and neuroimaging features of "idiopathic" syringomyelia

In some adult patients with cervical syringomyelia, MRI studies do not identify primary disease within the foramen magnum or spinal canal. To identify the etiology of this idiopathic type of syringomyelia, clinical features and posterior fossa (PF) measurements from 17 of these patients, 17 patients with Chiari I-type syringomyelia, and 32 control subjects were compared. Idiopathic syringomyelia and Chiari I-type syringomyelia manifested central cervical myelopathy and a small PF with narrow CSF spaces, suggesting that they develop by the same mechanism.

Detection of human herpesvirus-6 in mesial temporal lobe epilepsy surgical brain resections

BACKGROUND

Human herpesvirus-6 (HHV-6), a ubiquitous beta-herpesvirus, is the causative agent of roseola infantum and has been associated with a number of neurologic disorders including seizures, encephalitis/meningitis, and multiple sclerosis. Although the role of HHV-6 in human CNS disease remains to be fully defined, a number of studies have suggested that the CNS can be a site for persistent HHV-6 infection.

OBJECTIVE

To characterize the extent and distribution of HHV-6 in human glial cells from surgical brain resections of patients with mesial temporal lobe epilepsy (MTLE).

METHOD

Brain samples from eight patients with MTLE and seven patients with neocortical epilepsy (NE) undergoing surgical resection were quantitatively analyzed for the presence of HHV-6 DNA using a virus-specific real-time PCR assay. HHV-6 expression was also characterized by western blot analysis and in situ immunohistochemistry (IHC). In addition, HHV-6-reactive cells were analyzed for expression of glial fibrillary acidic protein (GFAP) by double immunofluorescence.

RESULTS

DNA obtained from four of eight patients with MTLE had significantly elevated levels of HHV-6 as quantified by real-time PCR. HHV-6 was not amplified in any of the seven patients with NE undergoing surgery. The highest levels of HHV-6 were demonstrated in hippocampal sections (up to 23,079 copies/10(6) cells) and subtyped as HHV-6B. Expression of HHV-6 was confirmed by western blot analysis and IHC. HHV-6 was co-localized to GFAP-positive cells that morphologically appeared to be astrocytes.

CONCLUSIONS

HHV-6B is present in brain specimens from a subset of patients with MTLE and localized to astrocytes in the absence of inflammation. The amplification of HHV-6 from hippocampal and temporal lobe astrocytes of MTLE warrants further investigation into the possible role of HHV-6 in the development of MTLE.

Retrospective analysis of surgical treatment outcomes for gelastic seizures: a review of the literature

Gelastic seizures are known to be refractory to medical treatment and to date surgical therapy has yet to pinpoint the best treatment for these refractory seizures. There has been a multitude of case reports published on gelastic seizures and different surgical treatments, thus we performed a review of the literature on gelastic seizures and surgical treatments to elucidate the best surgical approaches for medically refractory gelastic seizures.

Symptomatic vertebral hemangiomas: treatment by means of direct intralesional injection of ethanol

PURPOSE

To describe the technique and results of injecting ethanol directly into symptomatic vertebral hemangiomas.

MATERIALS AND METHODS

Eleven patients with paraplegia (n = 6) or radiculopathy (n = 5) due to vertebral hemangioma were treated by means of injecting ethanol (5-50 mL) directly into the lesion with computed tomographic (CT) guidance. CT angiograms were essential prior to treatment to identify functional vascular spaces of the hemangioma and direct needle placement.

RESULTS

All hemangiomas were obliterated completely at follow-up angiography and gadolinium-enhanced magnetic resonance imaging. Five of six patients with paraplegia recovered completely: One who was treated recently was walking with assistance. Four of five patients with radiculopathy improved. No immediate complications were associated with ethanol injection. The two patients who received the largest volumes of ethanol, 42 and 50 mL, developed pathologic fractures of the involved vertebrae 4 and 16 weeks after treatment.

CONCLUSION

Direct injection of ethanol into symptomatic vertebral hemangioma is an effective and safe treatment, provided the dose is less than 15 mL.

Spinal cord swelling preceding syrinx development. Case report

The pathophysiology of syrinx development is controversial. The authors report on a patient with progressive cervical myelopathy and a Chiari I malformation in whom spinal cord swelling preceded, by a few months, the development of a syrinx in the same location. The patient underwent a craniocervical decompressive procedure and duraplasty, and complete resolution of cord swelling and syringomyelia was achieved. This report is consistent with the theory that patients with Chiari I malformation have increased transmural flow of cerebrospinal fluid, which causes spinal cord swelling that later coalesces into a syrinx. The pathophysiology of syrinx development from spinal cord edema and the success of surgical decompressive treatments that do not invade the central nervous system support the prompt treatment of patients with spinal cord edema who are at risk for the development of a syrinx.

Elucidating the pathophysiology of syringomyelia

OBJECT

Syringomyelia causes progressive myelopathy. Most patients with syringomyelia have a Chiari I malformation of the cerebellar tonsils. Determination of the pathophysiological mechanisms underlying the progression of syringomyelia associated with the Chiari I malformation should improve strategies to halt progression of myelopathy.

METHODS

The authors prospectively studied 20 adult patients with both Chiari I malformation and symptomatic syringomyelia. Testing before surgery included the following: clinical examination; evaluation of anatomy by using T1-weighted magnetic resonance (MR) imaging; evaluation of the syrinx and cerebrospinal fluid (CSF) velocity and flow by using phase-contrast cine MR imaging; and evaluation of lumbar and cervical subarachnoid pressure at rest, during the Valsalva maneuver, during jugular compression, and following removal of CSF (CSF compliance measurement). During surgery, cardiac-gated ultrasonography and pressure measurements were obtained from the intracranial, cervical subarachnoid, and lumbar intrathecal spaces and syrinx. Six months after surgery, clinical examinations, MR imaging studies, and CSF pressure recordings were repeated. Clinical examinations and MR imaging studies were repeated annually. For comparison, 18 healthy volunteers underwent T1-weighted MR imaging, cine MR imaging, and cervical and lumbar subarachnoid pressure testing. Compared with healthy volunteers, before surgery, the patients had decreased anteroposterior diameters of the ventral and dorsal CSF spaces at the foramen magnum. In patients, CSF velocity at the foramen magnum was increased, but CSF flow was reduced. Transmission of intracranial pressure across the foramen magnum to the spinal subarachnoid space in response to jugular compression was partially obstructed. Spinal CSF compliance was reduced, whereas cervical subarachnoid pressure and pulse pressure were increased. Syrinx fluid flowed inferiorly during systole and superiorly during diastole on cine MR imaging. At surgery, the cerebellar tonsils abruptly descended during systole and ascended during diastole, and the upper pole of the syrinx contracted in a manner synchronous with tonsillar descent and with the peak systolic cervical subarachnoid pressure wave. Following surgery, the diameter of the CSF passages at the foramen magnum increased compared with preoperative values, and the maximum flow rate of CSF across the foramen magnum during systole increased. Transmission of pressure across the foramen magnum to the spinal subarachnoid space in response to jugular compression was normal and cervical subarachnoid mean pressure and pulse pressure decreased to normal. The maximum syrinx diameter decreased on MR imaging in all patients. Cine MR imaging documented reduced velocity and flow of the syrinx fluid. Clinical symptoms and signs improved or remained stable in all patients, and the tonsils resumed a normal shape.

CONCLUSIONS

The progression of syringomyelia associated with Chiari I malformation is produced by the action of the cerebellar tonsils, which partially occlude the subarachnoid space at the foramen magnum and act as a piston on the partially enclosed spinal subarachnoid space. This creates enlarged cervical subarachnoid pressure waves that compress the spinal cord from without, not from within, and propagate syrinx fluid caudally with each heartbeat, which leads to syrinx progression. The disappearance of the abnormal shape and position of the tonsils after simple decompressive extraarachnoidal surgery suggests that the Chiari I malformation of the cerebellar tonsils is acquired, not congenital. Surgery limited to suboccipital craniectomy, C-I laminectomy, and duraplasty eliminates this mechanism and eliminates syringomyelia and its progression without the risk of more invasive procedures.

Vascular endothelial growth factor (VEGF) modulates vascular permeability and inflammation in rat brain

Vascular endothelial growth factor (VEGF) is an angiogenic growth factor that also induces vascular permeability and macrophage migration. VEGF expression is weak in normal adult brain, but is strongly upregulated in glioma cells and reactive astrocytes, suggesting that chronic overexpression of VEGF in the brain contributes to blood-brain barrier (BBB) breakdown. We examined the effects of chronic VEGF overexposure on the integrity of the BBB using the following approaches: 1) continuous intracerebral infusion of VEGF via miniosmotic pump; and 2) intracerebral injection of an adenoviral vector encoding the VEGF165 gene (AdCMV.VEGF). After 6 days both treatments produced approximately 10-fold breakdown of the BBB (as measured by transport of 14C-aminoisobutyric acid (AIB) from blood into brain) compared with the respective controls (albumin infusion or AdCMV.beta gal virus). BBB disruption in AdCMV.VEGF-treated brains was accompanied by a severe inflammatory response not observed in brains receiving AdCMV.beta gal or VEGF protein infusion, indicating that neither VEGF nor viral particles alone were responsible for the inflammatory response. However, injection of AdCMV.beta gal followed by VEGF infusion to the same site also elicited inflammation. Chronic overexposure of normal brain to VEGF also increased intercellular adhesion molecule-1 (ICAM-1) and major histocompatibility complex (MHC) class I and II expression. Although VEGF itself is not inflammatory, VEGF may modulate immune responses in the central nervous system (CNS) by opening the BBB, altering the immunoprivileged status of the brain, and allowing contact between normally sequestered CNS antigens and blood-borne immune mediators.

Tumor devascularization by intratumoral ethanol injection during surgery. Technical note

Preoperative reduction in tumor vascularity has been accomplished previously by selective catheterization of tumor vessels and delivery of occlusive materials. The results of percutaneous infusion of vertebral hemangiomas and other vascular lesions led the authors to speculate that rapid devascularization of tumors by direct injection of ethanol (ETOH) could be used to reduce bleeding and facilitate resection during surgery. Thus, the use of intratumoral injection of ETOH and its effects on tumor hemostasis and resectability were examined. Four patients received direct injection of ETOH into either a spinal epidural (two renal cell carcinomas and one rhabdomyosarcoma) or a large cerebellar neoplasm (hemangioblastoma). Intraoperative perfusion of the tumors with ETOH produced immediate blanching and devascularization and enhanced visualization and resection. Incremental tumor devascularization is achieved by careful injection of small amounts of ETOH directly into the lesion, producing immediate and complete regional tumor devascularization. Use of this technique reduces intratumoral bleeding and enhances the ease and effectiveness of resection.

Vascular endothelial growth factor (vascular permeability factor) expression in injured rat brain

We investigated the expression of vascular endothelial growth factor (VEGF)/vascular permeability factor (VPF) in stab and freeze brain injury models in rats. Immunohistochemical staining with anti-VEGF antibodies demonstrated an increase in VEGF-positive cells in and around both lesions. Morphologically, the injury-induced VEGF-positive cells resembled astrocytes. Double immunofluorescent staining for the astrocytic marker glial fibrillary acidic protein (GFAP) and VEGF demonstrated directly that VEGF-positive cells which appeared in response to these injuries were astrocytes. VEGF expression in astrocytes was maximal on days 3 and 4 after injury in terms of both cell number and affected area. The increase in VEGF-positive cells was more widespread in the freeze lesion than in the stab wound, and occurred in both the lesioned and nonlesioned hemispheres. VEGF-positive cells were still present 3 weeks after both injuries, but their numbers were reduced and their distribution became limited to the immediate vicinity of the lesions. These observations indicate that astrocytes react to injury by increasing VEGF expression, suggesting that VEGF might participate in the central nervous system response to injury.

Mechanism of dexamethasone suppression of brain tumor-associated vascular permeability in rats. Involvement of the glucocorticoid receptor and vascular permeability factor

Brain tumor-associated cerebral edema arises because tumor capillaries lack normal blood-brain barrier function; vascular permeability factor (VPF, also known as vascular endothelial growth factor, VEGF) is a likely mediator of this phenomenon. Clinically, dexamethasone reduces brain tumor-associated vascular permeability through poorly understood mechanisms. Our goals were to determine if suppression of permeability by dexamethasone might involve inhibition of VPF action or expression, and if dexamethasone effects in this setting are mediated by the glucocorticoid receptor (GR). In two rat models of permeability (peripheral vascular permeability induced by intradermal injection of 9L glioma cell-conditioned medium or purified VPF, and intracerebral vascular permeability induced by implanted 9L glioma), dexamethasone suppressed permeability in a dose-dependent manner. Since 80% of the permeability-inducing activity in 9L-conditioned medium was removed by anti-VPF antibodies, we examined dexamethasone effects of VPF expression in 9L cells. Dexamethasone inhibited FCS- and PDGF-dependent induction of VPF expression. At all levels (intradermal, intracranial, and cell culture), dexamethasone effects were reversed by the GR antagonist mifepristone (RU486). Dexamethasone may decrease brain tumor-associated vascular permeability by two GR-dependent mechanisms: reduction of the response of the vasculature to tumor-derived permeability factors (including VPF), and reduction of VPF expression by tumor cells.

In vivo transfer of the human interleukin-2 gene: negative tumoricidal results in experimental brain tumors

The authors have recently shown the feasibility of eradicating brain tumors using in vivo retroviral-mediated transduction of tumors with the herpes simplex thymidine kinase (HStk) gene and ganciclovir therapy. However, thymidine kinase-transduced subcutaneous tumors in immunocompromised (athymic) mice were less responsive to this therapy than in immunocompetent animals, suggesting a role of the immune system in the process of tumor eradication. Broad suppression of humoral and cell-mediated immunity is found in patients with malignant gliomas. Interleukin-2 (IL-2) production and IL-2 receptor expression are decreased in gliomas patients. These findings and the proposed association between lymphocytic infiltration of brain tumors and survival suggest that immune response modifiers may be useful in treating glioma patients. To evaluate the role of local cytokine expression by tumor cells, alone or combined with HStk gene transfer and ganciclovir therapy, the authors investigated the efficacy of tumor (9L gliosarcoma) eradication in Fischer rats by in vitro and in vivo tumor transduction with the IL-2 gene alone or with a combined vector carrying both the HStk and IL-2 genes. Tumors injected with HStk vector-producer cells alone, with or without ganciclovir, and rats inoculated in the brain and subcutaneously with 9L cells that had previously been transduced in vitro served as controls. Murine vector-producer cells (3 x 10(6)/50 microliters) were injected into the brain tumors 7 days after tumor inoculation. Ganciclovir (15 mg/kg) was administered intraperitoneally twice daily for 10 days to animals that received HStk with or without IL-2 vector-producer cells, starting 5 days after producer-cell injection. The experiment was repeated with continuous daily treatment of all rats with oral dexamethasone (0.5 mg/kg). Rats were sacrificed 21 days after tumor inoculation, and the brains were removed for histological and immunohistochemical analysis for IL-2. Within each experimental group, tumors were found in a similar proportion in the dexamethasone-treated and untreated rats. Large brain tumors developed in all 10 rats that had been inoculated with 9L cells which had been pretransduced in vitro with the IL-2 gene, whereas only three of eight rats receiving subcutaneous inoculation of similar cells developed palpable tumors. No enhancement of tumor eradication was observed by adding the IL-2 gene in the HStk vector construct compared to the use of the vector with HStk alone. Lymphocytic infiltration was absent in all dexamethasone-treated rats but was observed in all treatment groups not receiving steroids.(ABSTRACT TRUNCATED AT 400 WORDS)

Persistent hypoglossal artery associated with basilar artery aneurysm

A saccular aneurysm at the tip of the basilar artery in a patient with a persistent hypoglossal artery is reported. The persistent hypoglossal artery was arising from the left internal carotid artery. Both vertebral and posterior communicating arteries were absent bilaterally. The combination of a persistent hypoglossal artery and a basilar bifurcation aneurysm is a very rare occurrence. The anatomy of the cerebral circulation in this unique case is important for surgical planning.