Neuronal desynchronization as a trigger for seizure generation.

Experimental reports have appeared which challenge the dogma that epileptic seizures arise as a consequence of neuronal hypersynchronization. We sought to explore what mechanisms that desynchronize neuronal firing could induce epileptic seizures. A computer model of connections in a mammalian hippocampal slice preparation was constructed including two recently-reported distinct inhibitory feedback circuits. When inhibition by interneurons that synapse on pyramidal dendrites was decreased, highly localized seizure-like bursting was observed in the CA3 region similar to that which occurs experimentally under GABAergic blockade. In contrast, when inhibition by interneurons that synapse in the axosomatic region was similarly decreased, no such bursting was observed. However, when this transient inhibition was increased, normal coordinated spread of excitation was interrupted by high-frequency localized seizure-like bursting. The increase of this inhibitory input resulted in decreased cell coupling of pyramidal neurons. A decrease in phase coherence was initially observed until seizure-like activity initiated causing a net increase in coherence as has been observed in epileptic patients. These results provide a possible pathway in which a decrease in synchronization could provide the trigger for inducing epileptiform activity.

Computer-assisted intraaneurysmal thrombus visualization.

OBJECTIVE: Improved visualization of intraaneurysmal thrombi can contribute to understanding their impact on clinical courses and treatments. Digital subtraction angiography (DSA) demonstrates the hemodynamic portion of aneurysm domes and vasculature structures and has been considered by many to be the principal technique used for aneurysm diagnosis. An intraaneurysmal thrombus may be visualized as a filling defect on DSA, but DSA does not reliably indicate the presence of an intraaneurysmal thrombus or its details. Computerized tomography (CT) and magnetic resonance (MR) imaging may have advantages over DSA, particularly because of their capacity to visualize soft tissue. Hence, we investigated the reconstruction of MR and CT images and compared it to DSA for assessment of intraaneurysmal thrombi. METHODS: Thirty-one patients with 34 aneurysms were enrolled. The entire group was examined with DSA. Sixteen cases were also examined with MR imaging; the remaining 15 were examined with CT imaging. Images of intraaneurysmal thrombi were rendered from corresponding MRI and soft tissue scans using CT. Intracranial vessels and aneurysms were defined from MR and CT angiography. Whole images were linked via imaging software for the reconstruction of vasculature structures. Images were superimposed to produce visualizations of thrombi situated in aneurysmal bodies. RESULTS: Reconstruction of the MR and CT images clearly demonstrated the presence and details of intraaneurysmal thrombi in 9 (26.4 %) of 34 aneurysms. DSA detected only 4 (11.7 %) of the cases as a filling defect. Significant differences in thrombus visualization were observed between DSA used alone or in conjunction with either MRA (P = .02) or CTA (P = .04) images. Mean volume of thrombosed aneurysms was 3.2 +/- 0.84 mL (mean +/- SEM) and thrombosis volume was 0.9 +/- 0.31 mL. Aneurysm and nested thrombus volumes were highly correlated (r = 0.987; P < .001). CONCLUSION: Intraaneurysmal thrombi were clearly visualized by computerized MR and CT image reconstruction. MR and CT were superior to DSA alone in demonstrating the presence of intra-aneurysmal thrombi. Computer-assisted 3-D visualization can be invaluable in understanding the shape and volume of intraaneurysmal thrombi, which may contribute to more accurate assessment and effective treatment of aneurysms cases.

Cervical foraminal area and intervertebral height changes after titanium ring cage placement: preliminary results.

OBJECTIVE: To investigate the effect of titanium ring cage implantation on cervical foraminal area and intervertebral height. METHODS: Twenty-two patients with single level cervical disc herniation were enrolled in this study. All patients underwent a standard anterior cervical discectomy followed by titanium ring cage implantation. Radiographs were used for evaluation of the cervical foraminal area and intervertebral height in the pre- and postoperative periods. RESULTS: Mean intervertebral heights were 0.7 +/- 0.1 cm (preoperative), 1.1 +/- 0.2 cm (early postoperative) and 0.9 +/- 0.2 (final measurement). Increase in intervertebral height at final follow-up was 0.2+/-0.1 cm (22.6+/-8.5%). Mean cervical foraminal areas were 0.4+/-0.1 cm2 (preoperative), 0.5 +/- 0.2 cm2 (early postoperative) and 0.5 +/- 0.1 cm2 (final measurement). Increase in cervical foraminal area at the final follow-up was 0.1 +/- 0.1 cm2. CONCLUSION: Our study demonstrates that cervical intervertebral height and cervical foraminal area significantly increased after cervical ring cage placement but subsidence during the follow-up period negatively affects foraminal area. However, overall, there was a relative increase of foraminal area and intervertebral height when compared with preoperative values. Long-term follow-up is required to further assess the subsidence rate.

Chlamydia pneumoniae infection related atherosclerotic clinical variables on carotid stenosis.

OBJECTIVE: Research results showed that Chlamydia pneumoniae infection is related to atherosclerosis. C. pneumoniae infection may exacerbate atherogenesis. We investigated the presence of this microorganism for patients who underwent carotid endarterectomy and evaluated clinical values of C. pneumoniae infection on carotid stenosis. METHODS: Twenty patients with carotid stenosis were enrolled in this prospective study between 1997 and 1999. The patients were observed on whether they were positive or negative in four C. pneumoniae measures, namely; IgA titers, IgG titers, presence of electron microscopy, and immunocytochemistry in the endarterectomy specimens. Possible clinical findings for atherosclerosis were also observed of Chlamydial measures such as the percentage of carotid stenosis, cholesterol and triglyceride levels, smoking status, symptomatic or non-transient ischaemic attack or stroke, previous ischaemic event, calcification at surgery, ulceration on angiographies, ulceration at surgery and hypertension were included in this evaluation. RESULTS: Specific C. pneumoniae IgG were detected as positive in 9 (45%) of 20 patient samples. These patients were regarded as having chronic Chlamydia pneumoniae infection. None of the patients were positive for IgA antibody. This result demonstrated no evidence of reinfection. Immunocytochemistry and electron microscopy were positive in 7 (35%) of the 20 patients and correlated with positive serological results. The proportion of previous ischaemic events, calcification at surgery, ulceration on angiography, and ulceration at surgery were found significantly higher ( p < 0.05 ) for patients who are positive for chlamydial measures than those who are negative. CONCLUSION: The results of this study demonstrated an association between C. pneumoniae to atherosclerosis. The proportion of patients who are positive for Chlamydia measures (IgG titers, electron microscopy, and immunocytochemistry) is significantly higher for those who were positive for each of these clinical variables (PIE, CALCI, U1, and U2) than who were negative. We emphasise, the higher incidence in clinical variables of PIE, CALCI, U1, and U2 in Chlamydia measures positive group may support the association of C. pneumoniae with atherosclerotic events.

Subthalamic and red nucleus volumes in patients with Parkinson's disease: do they change with disease progression?

OBJECTIVE: To examine a possible correlation between disease progression and the volumes of the subthalamic nucleus (STN) and red nucleus (RN) in patients with Parkinson disease (PD). METHODS: Twelve patients with PD (mean time since diagnosis 10.8 +/- 2.9 years) and age-matched 12 normal control subjects were enrolled. The volumes of the STN and RN were measured using 3-dimensional volume reconstructions of stereotactic magnetic resonance images. RESULTS: The PD and control groups were similar with regard to age and gender. The STN volume was 0.13 +/- 0.01 cm(3) (mean +/- SD) in PD patients and 0.27 +/- 0.01 cm(3) in controls (P < .001). The RN volume was 0.31 +/- 0.02 cm(3) in PD patients and 0.21 +/- 0.02 cm(3) in controls (P = .002). Positive correlations of RN volume with time since diagnosis (P = .004) and disease stage (P = .01) were observed. On average, the STN volumes were 48% smaller and RN volumes 32% larger in PD patients than in control subjects; the volumes of the two nuclei were negatively correlated (r = -0.46; P = .03). CONCLUSIONS: Our results suggest that advanced disease stage and longer disease duration are associated with increased RN volume. STN volume was significantly smaller in Parkinson group. These findings may be useful in estimating disease status and rate of progression, and may also have implications for surgical treatment. Larger studies are needed to validate these results and determine their usefulness.

De novo formation of cerebral cavernous malformation in a patient with intractable epilepsy: case report and review.

AIM: The exact origin and process of development of cerebral cavernous malformations (CCMs) is currently unknown. In this article, the authors present de novo CCM formation in a patient with intractable epilepsy and discuss the pathogenesis of CCM in light of several current theories. CASE DESCRIPTION: A 34-year-old man presented with a 10-year history of intractable seizures. His neurological examination was normal, and the initial magnetic resonance imaging (MRI) was suggestive of right mesial temporal sclerosis (MTS). Follow-up MRI study showed development of CCM in the right frontal region. Subsequently, invasive monitoring revealed right temporal seizure source, prompting right temporal lobectomy that resulted in abolition of epilepsy. Histological diagnosis of CCM was confirmed after the lesion was removed in a separate surgery. The patient recovered to normal lifestyle without any complications. CONCLUSION: This appears to be a first documented case of de novo CCM formation in the setting of intractable epilepsy with ipsilateral MTS. Since the possibility of lesion development cannot be ruled out based on clinical examination, updated imaging and thorough neurophysiological workup are needed for successful treatment of patients with intractable epilepsy.

Proportional feedback stimulation for seizure control in rats.

PURPOSE: A responsive electrical brain stimulation system using control feedback was investigated for the treatment of seizures. METHODS: A proportional feedback stimulation system was designed. Penicillin-induced episodic seizures were created in rat primary motor cortex. Both intracranial (proximal to seizure focus) and extracranial EEGs were monitored. Current stimulation was applied at the seizure focus by using the intracranial EEG as the current-stimulus template. Different gains (H) for determining feedback stimulus amplitudes were tested. RESULTS: The effect of feedback stimulation on seizures was initially assessed by measuring change in variance of the amplitude histogram of the intracranial EEG before and during stimulation. Mean reduction in amplitude variance during seizure activity was significant, with variance during stimulation progressively reduced as feedback gain was increased, indicating that overall suppression of seizure amplitude depended on H. Further increases in feedback gain typically produced saturating oscillations, indicating that this level of H resulted in instability. Frequency analysis of seizure and stimulation periods for each of the effective levels of H demonstrated close correlation across a large frequency domain, suggesting that the reduction in EEG seizure amplitude during feedback stimulation was possibly because of shunting of neuronal currents near electrodes as opposed to an alteration of neuronal dynamics. Although the frequency and energy responses during seizures before or during feedback stimulation remained well correlated in the delta band, this correlation progressively decreased across the theta, alpha, and beta bands. CONCLUSIONS: These results demonstrate that proportional feedback stimulation holds the promise of suppressing seizure activity. More-complicated control algorithms for generating feedback stimulation may provide further improvements in seizure suppression.

Chiari type I malformation presenting as hemifacial spasm: case report.

OBJECTIVE AND IMPORTANCE: We report on a patient with a Chiari I malformation presenting with right hemifacial spasm. Clinicians should consider the downward displacement of the hindbrain as a rare cause of hemifacial spasm in Chiari I malformation. CLINICAL PRESENTATION: An 18-year-old man was admitted with right hemifacial spasm. The results of the neurological examination were normal except for the facial spasm. Magnetic resonance imaging demonstrated a Chiari I malformation without syringomyelia. After surgery, the hemifacial spasm completely resolved. INTERVENTION: Posterior fossa decompression, C1 laminectomy, and duraplasty were performed. CONCLUSION: The hemifacial spasm could be attributed to compression and/or traction of the facial nerve because of downward displacement of the hindbrain in Chiari I malformation. Compression and/or traction might create irritation of the facial nerve that causes hemifacial spasm. Resolution of the hemifacial spasm after posterior fossa decompression could explain the facial nerve irritation in Chiari I malformation. Clinicians should consider Chiari malformation as a cause of hemifacial spasm and posterior fossa decompression as a potential treatment.

Bilateral reversible deafness after surgery for unilateral epidermoid tumor: an unusual complication: case report.

OBJECTIVE AND IMPORTANCE: We present an unusual complication of bilateral hearing loss after surgery for unilateral epidermoid tumor situated at the right pontocerebellar junction. The neurosurgeon must know the possible causes of this catastrophic complication and should take every possible measure to avoid it. CLINICAL PRESENTATION: A 43-year-old male patient presented with progressive hearing loss in the right ear. A radiological examination demonstrated a mass lesion at the right pontocerebellar junction. A pure tone audiogram revealed sensorineural hearing impairment of the right ear. A brainstem auditory evoked potential test confirmed this with reduced amplitudes and a prolonged I-V interval. INTERVENTION: The patient was operated on via a right paramedian suboccipital craniectomy. The tumor was completely excised, and all of the cranial nerves were preserved during the operation. Postoperatively, the patient developed total bilateral hearing loss, which improved significantly over time. CONCLUSION: Controlled cerebrospinal fluid drainage during exposure and tumor excision may reduce the possibility of shift and traction on the neural structures and help to prevent ischemic injury. Frequent irrigation of the surgical field and minimizing the spilling of the tumor contents may reduce the risk of chemical irritation. The use of corticosteroids may also help during the postoperative period.