Arul Bala

Accuracy of Postoperative Computed Tomography and Magnetic Resonance Image Fusion for Assessing Deep Brain Stimulation Electrodes

BACKGROUND:Knowledge of the anatomic location of the deep brain stimulation (DBS) electrode in the brain is essential in quality control and judicious selection of stimulation parameters. Postoperative computed tomography (CT) imaging coregistered with preoperative magnetic resonance imaging (MRI) is commonly used to document the electrode location safely. The accuracy of this method, however, depends on many factors, including the quality of the source images, the area of signal artifact created by the DBS lead, and the fusion algorithm. OBJECTIVE:To calculate the accuracy of determining the location of active contacts of the DBS electrode by coregistering postoperative CT image to intraoperative MRI. METHODS:Intraoperative MRI with a surrogate marker (carbothane stylette) was digitally coregistered with postoperative CT with DBS electrodes in 8 consecutive patients. The location of the active contact of the DBS electrode was calculated in the stereotactic frame space, and the discrepancy between the 2 images was assessed. RESULTS:The carbothane stylette significantly reduces the signal void on the MRI to a mean diameter of 1.4 ± 0.1 mm. The discrepancy between the CT and MRI coregistration in assessing the active contact location of the DBS lead is 1.6 ± 0.2 mm, P < .001 with iPlan (BrainLab AG, Erlangen, Germany) and 1.5 ± 0.2 mm, P < .001 with Framelink (Medtronic, Minneapolis, Minnesota) software. CONCLUSION:CT/MRI coregistration is an acceptable method of identifying the anatomic location of DBS electrode and active contacts.

Accuracy of magnetic resonance imaging-directed frame-based stereotaxis.

BACKGROUND: Accurate placement of a probe to the deep regions of the brain is an important part of neurosurgery. In the modern era, magnetic resonance image (MRI)-based target planning with frame-based stereotaxis is the most common technique. OBJECTIVE: To quantify the inaccuracy in MRI-guided frame-based stereotaxis and to assess the relative contributions of frame movements and MRI distortion. METHODS: The MRI-directed implantable guide-tube technique was used to place carbothane stylettes before implantation of the deep brain stimulation electrodes. The coordinates of target, dural entry point, and other brain landmarks were compared between preoperative and intraoperative MRIs to determine the inaccuracy. RESULTS: The mean 3-dimensional inaccuracy of the stylette at the target was 1.8 mm (95% confidence interval [CI], 1.5-2.1. In deep brain stimulation surgery, the accuracy in the x and y (axial) planes is important; the mean axial inaccuracy was 1.4 mm (95% CI, 1.1-1.8). The maximal mean deviation of the head frame compared with brain over 24.1 ± 1.8 hours was 0.9 mm (95% CI, 0.5-1.1). The mean 3-dimensional inaccuracy of the dural entry point of the stylette was 1.8 mm (95% CI, 1.5-2.1), which is identical to that of the target. CONCLUSION: Stylette positions did deviate from the plan, albeit by 1.4 mm in the axial plane and 1.8 mm in 3-dimensional space. There was no difference between the accuracies at the dura and the target approximately 70 mm deep in the brain, suggesting potential feasibility for accurate planning along the whole trajectory.

Delayed pneumocephalus following shunting for hydrocephalus

Delayed pneumocephalus is a rare but well-reported complication of cerebrospinal fluid diversion procedures. In most cases the air enters the intracranial cavity via a skull base defect. We report a case of hydrocephalus secondary to aqueduct stenosis. The patient developed pneumocephalus 2 months after successful placement of a ventriculoperitoneal shunt. We describe an attempt at endoscopic diagnosis and repair of the fistula. This was unsuccessful, presumably because the defect was too small to localize even with the use of intrathecal fluorescein. We subsequently performed a conventional craniotomy and anterior fossa repair with placement of an antisiphon device. We suggest that in certain cases, when patients present with long-standing hydrocephalus, it may be advisable to insert either a high-pressure valve or antisiphon device as a primary measure.

Longitudinal clivus fracture associated with trapped basilar artery: unusual survival with good neurological recovery.

A 46-year-old motorcyclist sustained severe cranio-facial fractures from a fall at 60 km/h. He gradually developed a left hemiparesis and diplopia but retained a GCS of 15. CT head scan revealed a longitudinal clivus fracture. MRA of intracranial vessels identified a trapped basilar artery. The patient made an excellent recovery with residual left abducens palsy on follow-up at 10 weeks. Such recovery with minimal residual deficit in the context of this injury has not previously been reported. Reported cases to date are reviewed and causative mechanisms discussed.

High-frequency pallidal stimulation for camptocormia in Parkinson disease: case report.

BACKGROUND AND IMPORTANCE:Camptocormia is characterized by abnormal flexion of the thoracolumbar spine that increases during upright posture and abates in the recumbent position and has been reported to occur in patients with Parkinson disease. Camptocormia causes significant spinal and abdominal pain, impairment of balance, and social stigma. CLINICAL PRESENTATION:A 57-year-old woman with Parkinson disease developed severe camptocormia, which did not improve with trials of antiparkinsonian and muscle relaxant medications. The patient was successfully treated with bilateral globus pallidus interna deep brain stimulation surgery under general anesthesia. High-frequency neuromodulation afforded relief of camptocormia and improvement in Parkinson disease symptoms. CONCLUSION:Camptocormia in Parkinson disease may represent a form of dystonia and can be treated effectively with chronic pallidal neuromodulation.

Does remote ischemic preconditioning prevent delayed hippocampal neuronal death following transient global cerebral ischemia in rats

Objective: To determine if remote ischemic preconditioning (RIPC) induced by transient limb ischemia is protective against delayed hippocampal neuronal death in rats undergoing transient global cerebral ischemia (GCI). Method: Animals were randomized into 3 groups: Group I (Control, n = 5) underwent sham procedure, namely, general anesthesia x 2, without cerebral ischemia; Group II (RIPC + GCI, n = 5) was subjected to RIPC, induced by transient left hind limb ischemia under general anesthesia prior to GCI; Group III (GCI only, n = 5) underwent sham procedure under general anesthesia prior to GCI. Twenty-four hours after the RIPC or sham procedure, a transient GCI was induced for 8 minutes in Groups II and III by means of bilateral common carotid artery occlusion and hypotension. Hippocampal CA1 neurons were histologically examined at 7 days after ischemia. Results: There was no significant difference between the RIPC group and the ischemia only group. The number of neurons in the RIPC group were 0.90 (95% CI 0.20, 4.08) times the number in the ischemia group (p=0.89). The number of neurons in the RIPC group were 0.03 (95% CI 0.01, 0.10) times the number in the Control group (p=0.0001). Conclusion: Second window of the RIPC does not prevent hippocampal CA1 neuronal death at 7 days after transient global cerebral ischemia.

Spinal chondromyxoid fibroma of C2.

Chondromyxoid fibroma of bone (CMF) is a rare benign primary bone neoplasm accounting for less than 0.5% of all primary bone neoplasms. The spine is an uncommon site for this tumour, with forty-two cases reported in the modern English literature. They have clinical features similar to CMF arising at other sites. Local recurrence is well documented. We report an incidentally discovered lytic lesion of the C2 vertebra. The patient underwent stereotactic CT guided trans-oral curettage of the lesion with iliac bone graft and anterior fusion of C2 and C3. Microscopic examination of the surgical specimen demonstrated CMF. This is the second reported case of this rare tumour in this location. We review the literature and the unique radiological and pathological features and management of spinal CMF. Local recurrence of spinal CMF and its management is also discussed in light of the five previously reported cases of local spinal recurrence.

Spinal subarachnoid hemorrhage secondary to rupture of an isolated radicular artery aneurysm.

Aneurysmal subarachnoid hemorrhage (aSAH) of spinal origin is an uncommon entity and comprises less than 1% of all aSAH. The paucity of clinical cases creates challenges to its diagnosis and management. We present the case of a 58-year-old male, who presented with a spinal subarachnoid hemorrhage secondary to a de novo spinal radicular artery aneurysm. Spinal subarachnoid hemorrhages typically occur secondary to arteriovenous malformations or arterial wall weakness seen in collagen vascular disease. Fewer than 20 cases of isolated spinal arterial aneurysms have been published. SAHs of spinal origin are exceedingly rare and thus a high index of suspicion is required for an accurate and timely diagnosis.

Author response: retinal vein pulsation is in phase with intracranial pressure and not intraocular pressure.

We appreciate the comments by Jonas et al. concerning our recent paper. It is worth noting that we were unable to measure the shape of the IOP curve; however, in general terms it has a more sine-wave–like shape than intracranial pressure (ICP) curves. ICP curves have a steep rising phase and more gentle but variable downward phase, being derived largely from the large arterial pulse characteristics. It is also worth noting that our ICP recordings measure intracranial cerebrospinal fluid (CSF) pressure and that we have made the assumption that it is transmitted with a similar pulse curve into the optic nerve subarachnoid space. It seems likely that just after diastole, as pressures are rising, the IOP is not rising as quickly as ICP, and during this phase the pressure difference between IOP and CSF in the optic nerve subarachnoid space is reduced. From our earlier servo-null tissue pressure measurements in dogs, we know that retrolaminar tissue pressure pulse closely follows the CSF pressure pulse. The translaminar pressure gradient is dependent upon the difference between IOP and retrolaminar tissue pressure. As Jonas et al. postulate, the observed pulse relationship may reduce the energy requirement for retrograde axonal transport up the translaminar pressure gradient during the upward phase of the pressure cycle. We cannot predict the likely relationship during the downward phase, mainly because the ICP pressure curve varies greatly during this phase. William Morgan Christopher Lind Samuel Kain Naeem Fatehee Arul Bala Dao-Yi Yu