The Magnetic Resonance Imaging (MRI)-Directed Implantable Guide Tube Technique: Accuracy and Applications in Deep Brain Stimulation.

OBJECTIVE: The magnetic resonance imaging (MRI)-directed implantable guide tube technique allows for direct targeting of deep brain structures without microelectrode recording or intraoperative clinical assessment. This study describes a 10-year institutional experience of this technique including nuances that enable performance of surgery using readily available equipment. METHODS: Eighty-seven patients underwent deep brain stimulation surgery using the guide tube technique for Parkinson disease (n = 59), essential tremor (n = 16), and dystonia (n = 12). Preoperative and intraoperative MRI was analyzed to measure lead accuracy, volume of pneumocephalus, and the ability to safely plan a trajectory for multiple electrode contacts. RESULTS: Mean target error was measured to be 0.7 mm (95% confidence interval [CI] 0.6-0.8 mm) in the anteroposterior plane, 0.6 mm (95% CI 0.5-0.7 mm) in the mediolateral plane, and 0.8 mm (95% CI 0.7-0.9 mm) in the superoinferior plane. Net deviation (Euclidean error) from the planned target was 1.3 mm (95% CI 1.2-1.4 mm). Mean intracranial air volume per lead was 0.2 mL (95% CI 0.1-0.4 mL). In total, 52 patients had no intracranial air on postoperative imaging. In all patients, a safe trajectory could be planned to target for multiple electrode contacts without violating critical neural structures, the lateral ventricle, sulci, or cerebral blood vessels. CONCLUSIONS: The MRI-directed implantable guide tube technique is a highly accurate, low-cost, reliable method for introducing deep brain electrodes. This technique reduces brain shift secondary to pneumocephalus and allows for whole trajectory planning of multiple electrode contacts.

Endodermal Cyst Arising from the Oculomotor Nerve: A Case Report Outlining the Novel Insertion of Cysto-subarachnoid Shunt for Refractory Disease.

BACKGROUND: Endodermal cysts of the oculomotor nerve are rare presentations. Only case reports are available to help guide clinicians with managing this rare entity. CASE DESCRIPTION: A 3-year-old boy presented with an acute on chronic left oculomotor nerve palsy due to a left interpeduncular cistern cyst found on magnetic resonance imaging. He underwent a left pterional craniotomy and fenestration of the histologically proven endodermal cyst and had initial improvement at the 2-month review. He subsequently developed clinical and radiologic evidence of recurrence and was treated surgically with a refenestration and insertion of a cysto-subarachnoid shunt through a trans-sylvian approach. At 6-month follow-up, there was complete resolution of the oculomotor nerve palsy with interval development of oculomotor synkinesis. CONCLUSIONS: Magnetic resonance imaging is an essential modality in the follow-up of these patients postoperatively in the setting of unchanged or deteriorated neurology. Fenestration of the cyst is appropriate first-line surgical management; however, a cysto-subarachnoid shunt is a safe consideration in recurrent, symptomatic cysts and provides sustained symptom resolution.

Infantile Optic Pathway Glioblastoma.

BACKGROUND: Optic pathway gliomas and glioblastomas remain a rare entity within the infant population. CASE DESCRIPTION: We outline the case of a 6-month-old female who presented with failure to thrive, nystagmus and features of raised intracranial pressure. Subsequent magnetic resonance imaging demonstrated an infiltrating tumor radiating from the optic nerves bilaterally. She underwent emergent ventriculoperitoneal shunting and biopsy. Histology confirmed a World Health Organization grade IV glioblastoma. CONCLUSIONS: The patient remained clinically and radiologically stable at 1 year. Optic pathway glioblastoma in this population is a previously undescribed entity that requires multidisciplinary input to guide ongoing therapy.

Surgical Management of Spontaneous Spinal Cerebrospinal Fluid Epidural Fistula.

BACKGROUND: Intracranial hypotension secondary to spontaneous spinal cerebrospinal fluid (CSF) fistula is a rare condition that can have serious sequelae. Early diagnosis and treatment can be challenging. CASE DESCRIPTION: We present the case of a 17-year-old male who presented with a history of sudden-onset, postural headaches associated with upper thoracic back pain. Magnetic resonance imaging (MRI) demonstrated a thoracic extradural fluid collection and slumping of the brain within the posterior fossa. The patient was initially managed with a period of bed rest, followed by a thoracic epidural blood patch. Symptoms recurred and subsequent operative exploration found a large arachnoid cyst with CSF egress through a linear split in the axilla of the right T7 nerve root. The arachnoid cyst was resected, and the defect was closed primarily. All symptoms completely resolved. MRI at 3 months postoperatively demonstrated normal spinal configuration and resolution of brain sagging. CONCLUSIONS: Spontaneous CSF leaks are a rare cause of postural headache. Although epidural blood patching is an easy and safe intervention, early serial imaging to ascertain the evolution of the pathology may identify cases that are amenable to early surgical management.

Thoracic discectomy by posterior pedicle-sparing, transfacet approach with real-time intraoperative ultrasonography: Clinical article.

OBJECT: Symptomatic thoracic disc herniations (TDHs) are relatively uncommon, and the technical challenges of resecting the offending disc are formidable due to the location of spinal cord that has relatively poor perfusion characteristics within a narrow canal. The majority of disc herniations are long-standing calcified discs that can be adherent to the ventral dura. Real-time intraoperative ultrasound (RIOUS) visualization of the spinal cord during the retraction and resection of the disc greatly enhances the safety and efficacy of disc resection. The authors have adopted the posterior laminectomy with pedicle-sparing transfacet approach with real-time ultrasound guidance in their practice, and they present the clinical outcome in their patients to illustrate the safety profile of this technique. METHODS: Sixteen consecutive patients undergoing operative management of TDHs were identified from the authors' database. All patients underwent microdiscectomy through a posterior transfacet pedicle-sparing approach under RIOUS. Outcomes and complications were retrospectively assessed in this patient series. Clinical records and pre- and postoperative imaging studies were scrutinized to assess levels and types of disc herniation, blood loss, surgical time, pre- and postoperative Nurick grades, Japanese Orthopaedic Association (JOA) scores, and complications. RESULTS: All patients had single-level symptomatic TDHs. The patients presented with symptoms including thoracic myelopathy, axial back pain, urinary symptoms, and thoracic radiculopathy. Thoracic disc herniations involved levels T2-3 to T12-L1. Discs were classified as central or paracentral, and as calcified or noncalcified. All discs were successfully removed with no incidence of neural injury or CSF leak. The mean estimated blood loss was 523 ml, and the mean surgical time was 159 minutes. Nurick grades improved on average from 3.3 to 1.6. The mean JOA scores improved from 5.7 to 8.3 out of 11. The mean Hirabayashi recovery rate of the JOA score was 57%. All patients reported improvement in symptoms compared with preoperative status except for 1 patient with an American Spinal Injury Association Grade A spinal cord injury prior to surgery. The average duration of follow-up was 10.5 months. One patient developed postoperative wound infection that required additional operative debridement and revision of hardware. CONCLUSIONS: Thoracic discectomy via a posterior pedicle-sparing transfacet approach is an adequate method of managing herniations at any thoracic level. The safety of the operation is significantly enhanced by the use of realtime intraoperative ultrasonography.

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.

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.

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.