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Nurdin A. Kadyrov, Jonathan A. Friedman, Douglas A. Nichols, Aaron A. Cohen-Gadol, Michael J. Link and David G. Piepgras

✓ Internal carotid artery (ICA) pseudoaneurysm formation following transsphenoidal surgery is a rare but potentially lethal complication. Direct surgical repair with preservation of the ICA may be difficult. The feasibility of endovascular coil embolization with parent artery preservation for an iatrogenic ICA pseudoaneurysm is undefined.

A 40-year-old man was referred to the authors' institution after identification of a pseudoaneurysm of the left ICA following transsphenoidal resection of a pituitary macroadenoma. The pseudoaneurysm was treated via an endovascular approach that included stent-assisted coil embolization of the lesion. Follow-up angiographic studies obtained 1 year later demonstrated complete occlusion of the aneurysm, and the patient remains asymptomatic.

Stent-assisted coil embolization of this iatrogenic pseudoaneurysm was successful in achieving complete, angiographically confirmed aneurysm obliteration, with preservation of the ICA and short-term prevention of hemorrhage or carotid—cavernous fistula. The endovascular method provided an effective, relatively low-risk treatment for this difficult lesion, and was an excellent alternative to direct surgical repair. Nonetheless, long-term follow-up review is required before definitive treatment recommendations can be made.

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Aaron A. Cohen-Gadol, Jeffrey W. Britton, Clifford R. Jack Jr., Jonathan A. Friedman and W. Richard Marsh

✓ Transient neuroimaging abnormalities associated with seizure activity have received little attention in the literature. The authors report a focal magnetic resonance (MR) imaging abnormality of the corpus callosum in a patient following a secondary generalized seizure. A 27-year-old right-handed man presented with a history of medically refractory partial seizures since the age of 1 year. The results of an MR imaging study obtained 4 months prior to the patient undergoing video-electroencephalography monitoring were unremarkable. After the patient discontinued all antiepileptic medications, a secondary generalized seizure of right temporal origin was recorded. Five days later, repeated MR imaging revealed a nonenhancing 14 × 11—mm ovoid hyperintense lesion in the splenium of corpus callosum. The patient was asymptomatic, and his neurological and neurocognitive examinations remained unremarkable. Follow-up MR imaging 5 weeks and 1 year later demonstrated near-complete resolution of the lesion. Benign and transient abnormalities in the splenium can occur as a periictal phenomenon. A high index of suspicion and follow-up imaging may prevent further unwarranted intervention.

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Robert D. Ecker, Stephan J. Goerss, Fredric B. Meyer, Aaron A. Cohen-Gadol, Jeffrey W. Britton and James A. Levine

✓ High-resolution dynamic infrared (DIR) imaging provides intraoperative real-time physiological, anatomical, and pathological information; however, DIR imaging has rarely been used in neurosurgical patients. The authors report on their initial experience with intraoperative DIR imaging in 30 such patients.

A novel, long-wave (8–10 µm), narrow-band, focal-plane-array infrared photodetector was incorporated into a camera system with a temperature resolution of 0.006°C, providing 65,000 pixels/frame at a data acquisition rate of 200 frames/second. Intraoperative imaging of patients was performed before and after surgery. Infrared data were subsequently analyzed by examining absolute differences in cortical temperatures, changes in temperature over time, and infrared intensities at varying physiological frequencies.

Dynamic infrared imaging was applied in a variety of neurosurgical cases. After resection of an arteriovenous malformation, there was postoperative hyperperfusion of the surrounding brain parenchyma, which was consistent with a loss of autoregulation. Bypass patency and increased perfusion of adjacent brain were documented during two of three extracranial—intracranial bypasses. In seven of nine patients with epilepsy the results of DIR imaging corresponded to seizure foci that had been electrocorticographically mapped preoperatively. Dynamic infrared imaging demonstrated the functional cortex in four of nine patients undergoing awake resection and cortical stimulation. Finally, DIR imaging exhibited the distinct thermal footprints of 14 of 16 brain tumors.

Dynamic infrared imaging may prove to be a powerful adjunctive intraoperative diagnostic tool in the neurosurgical imaging armamentarium. Real-time assessment of cerebral vessel patency and cerebral perfusion are the most direct applications of this technology. Uses of this imaging modality in the localization of epileptic foci, identification of functional cortex during awake craniotomy, and determination of tumor border and intraoperative brain shift are avenues of inquiry that require further investigation.

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Tomohiro Inoue, Aaron A. Cohen-Gadol and William E. Krauss

✓ Almost 40 cases of spontaneous transdural spinal cord herniation have been reported in the literature. These patients often present with gait disturbance and sensory changes, and their condition is diagnosed as Brown—Séquard syndrome. The pathogenesis of this condition has remained poorly understood. In particular, there is no agreement whether the dural defect is acquired or congenital. In the reported case, a 21-year-old man presented with a 3-year history of intermittent low-pressure headaches consistent with intracranial hypotension. Eventually, the headaches resolved but he developed myelopathy due to a spinal cord herniation. In this case, the authors hypothesize that the progressive spinal cord herniation through a spontaneous dural tear sealed the site of the cerebrospinal fluid leak, causing the resolution of headaches.

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Aaron A. Cohen-Gadol, Mark B. Dekutoski, Choll W. Kim, Lynn M. Quast and William E. Krauss

Object. The AO Universal Spine System thoracic pedicle hook design includes a fixation screw that passes obliquely through the inferior facet into the pedicle to engage in the posterior portion of the superior vertebral body endplate. This endplate screw provides additional purchase at the hook—bone interface. To determine the safety of this fixation system the authors reviewed the operative notes, radiographs, and outcomes of patients who underwent placement of endplate screws.

Methods. Thirty-six patients (16 male and 20 female patients) who required posterior thoracic instrumentation for spinal deformity (11 cases), neoplasm (15 cases), and traumatic injury (10 cases) were included in this study.

One hundred sixty-four endplate screws were placed (mean 4.3/patient) to augment pedicle hooks for posterior thoracic instrumentation. The number of instrumented levels ranged from seven to 16. The positions of the screws in relation to the pedicle, neural foramen, spinal canal, and endplate were evaluated by assessing plain radiographs and computerized tomography scans (10 cases). Eighty-two screws (56%) were in ideal position. Lateral pedicle wall perforation occurred with 51 screws (35%). Three screws violated the medial wall and nine screws violated the superior or inferior walls of the pedicle. There were no clinical sequelae associated with any of the malpositioned screws. Adequate follow-up radiographic data were not available in five patients. The mean follow-up duration was 19.8 months (range 3–61 months).

Two patients required revision surgery at 3 months and 18 months, respectively, because of hook/endplate screw displacement. There was also one case of an endplate screw fracture without hook displacement that was discovered during subsequent revision surgery. The remainder of the endplate screws and associated pedicles hooks maintained their original positions. There was no case of spinal cord, nerve root, pulmonary, or vascular injury.

Conclusions. The placement of supplemental endplate screws in conjunction with thoracic pedicle hooks can be conducted safely.

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Aaron A. Cohen-Gadol, Ofer M. Zikel, Cody A. Koch, Bernd W. Scheithauer and William E. Krauss

Object. Spinal meningiomas occur most frequently in older patients. They are well-circumscribed and slow-growing tumors that are associated with good patient outcomes following surgery. Spinal meningiomas occurring in younger patients may be more aggressive, with a worse prognosis. The authors present their 21-year experience with spinal meningiomas in patients younger than 50 years of age.

Methods. The authors reviewed data obtained in 40 patients (age < 50 years) treated at the Mayo Clinic, Rochester, during the past 21 years; in all cases the lesions were histologically confirmed spinal meningiomas. Five men (12.5%) and 35 women (87.5%) (mean age 34.5 ± 10.9 years) underwent 52 operations for 41 tumors. The mean follow-up duration was 82 ± 93 months (range 0–445 months). The data obtained in these patients were compared with those derived from a random control cohort of 40 patients older than age 50 years in whom spinal meningiomas were resected at the Mayo Clinic during a similar period. In this cohort, there were 33 women and seven men whose mean age was 67.1 ± 9.5 years. The mean follow-up duration for the older group was 88 ± 72.3 months (range 18–309 months).

Compared with the random cohort of older patients, younger patients there tended to have more tumors located in the cervical spine (39%) as well as a greater number of predisposing factors such as neurofibromatosis Type 2, radiation exposure, or trauma. Nine (22%) of the patients younger than 50 years of age required reoperation for residual or recurrent tumor compared with two (5%) in the older patient control group. The overall mortality rate at the completion of the study for the younger patients was 10%.

Conclusions. Spinal meningiomas in younger patients have a worse prognosis than similar tumors in older patients.

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Aaron A. Cohen-Gadol, Jeffrey W. Britton, Frederic P. Collignon, Lisa M. Bates, Gregory D. Cascino and Fredric B. Meyer

Object. Surgical treatment options for intractable seizures caused by a nonlesional epileptogenic focus located in the central sulcus region are limited. The authors describe an alternative surgical approach for treating medically refractory nonlesional perirolandic epilepsy.

Methods. Five consecutive patients who were treated between 1996 and 2000 for nonlesional partial epilepsy that had originated in the central lobule were studied. The patients' ages ranged from 16 to 56 years (mean 28.6 years; there were four men and one woman). The duration of their epilepsy ranged from 8 to 39 years (mean 20.2 years), with a mean seizure frequency of 19 partial seizures per week. Preoperative assessment included video electroencephalography (EEG) and subtracted ictal—interictal single-photon emission computerized tomography coregistered with magnetic resonance imaging (SISCOM). Patients underwent an awake craniotomy stereotactically guided by the ictal EEG and SISCOM studies. Cortical stimulation was used to identify the sensorimotor cortex and to reproduce the patient's aura. A subdural grid was then implanted based on these results. Subsequent postoperative ictal electrocorticographic recordings and cortical stimulation further delineated the site of seizure onset and functional anatomy. During a second awake craniotomy, a limited resection of the epileptogenic central lobule region was performed while function was continuously monitored intraoperatively. One resection was limited to the precentral gyrus, two to the postcentral gyrus, and in two the excisions involved regions of both the pre- and postcentral gyri.

In three patients a hemiparesis occurred postsurgery but later resolved. In the four patients whose resection involved the postcentral gyrus, transient cortical sensory loss and apraxia occurred, which completely resolved in three. Two patients are completely seizure free, two have experienced occasional nondisabling seizures, and one patient has benefited from a more than 75% reduction in seizure frequency. The follow-up period ranged from 2 to 5.5 years (mean 3.5 years).

Conclusions. A limited resection of the sensorimotor cortex may be performed with acceptable neurological morbidity in patients with medically refractory perirolandic epilepsy. This procedure is an alternative to multiple subpial transections in the surgical management of intractable nonlesional epilepsy originating from the sensorimotor cortex.

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Aaron A. Cohen-Gadol, J. Eric Ahlskog, Joseph Y. Matsumoto, Mary A. Swenson, Robyn L. McClelland and Dudley H. Davis

Object. Selective peripheral denervation is currently the primary surgical treatment for intractable cervical dystonia. The authors assessed preoperative factors to determine which, if any, correlated with outcomes in patients with torticollis who had undergone this procedure.

Methods. The records of 168 consecutive patients who had undergone selective peripheral denervation for cervical dystonia between 1988 and 1996 at the Mayo Clinic were reviewed. There were 89 women (53%) and 79 men (47%) with a mean age of 53.4 years. Selection of muscles for denervation was based on the patient's clinical presentation and electromyography mapping results. The most common torticollis vectors were rotational in 141 patients (84%) and laterocollis in 59 (35%). Seventy patients (42%) presented with combined vectors. The technique used to remedy both conditions involved denervation of the ipsilateral posterior cervical paraspinal and splenius capitis muscles. Denervation of the sternocleidomastoid muscle was performed on the contralateral side for rotational torticollis and on the ipsilateral side for laterocollis. A rigorous physical therapy program followed surgery.

At the 3-month postoperative evaluation, 125 patients (77%) of the 162 who were available for follow up had moderate to excellent improvement in their head position, and pain was moderately to markedly improved in 131 patients (81%). The long-term follow up lasted a mean of 3.4 years and was undertaken in 130 patients. The original level of moderate to excellent improvement in head position and pain was retained in at least 71 patients (70%). Outcome was not predicted by preoperative head position, severity of abnormal posture of head, symptom duration, presence of tremor or phasic dystonic movements, or failure to respond to botulinum toxin treatment. Five patients recovered from postoperative complications including one myocardial infarction, one pulmonary embolism, and three respiratory failures. Three patients suffered from persistent C-2 distribution dysesthesias and three from slight shoulder weakness; one had a wound infection, and one died of respiratory arrest.

Conclusions. Selective peripheral denervation is an effective method of achieving lasting improvement of dystonia in most patients with intractable torticollis.

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Aaron A. Cohen-Gadol, Jacqueline A. Leavitt, James J. Lynch, W. Richard Marsh and Gregory D. Cascino

Object. In this prospective study the authors investigated the incidence and natural history of postoperative diplopia in patients undergoing anterior temporal lobectomy (ATL) and amygdalohippocampectomy for medically intractable mesial temporal lobe epilepsy.

Methods. Forty-seven patients scheduled for ATL for medically refractory seizures were examined preoperatively, 2 to 7 days postoperatively, and 3 to 6 months postoperatively. Ophthalmological examination including pupillary measurements, stereoacuity measurements, palpebral fissure measurements, vertical fusional amplitudes, Lancaster red green testing, visual field testing, and alternate cover testing was performed. Antiepileptic drug levels were monitored.

Nine (19%) of 47 patients developed diplopia postoperatively. The diplopia was caused by trochlear nerve palsy in every case. No oculomotor nerve dysfunction was documented. Trochlear nerve function recovered completely in all patients within 3 to 6 months postoperatively.

Conclusions. Postoperative diplopia following ATL occurs more often than previously thought and is primarily due to trochlear nerve dysfunction. Awareness of this transient complication is important in preoperative patient counseling.

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Aaron A. Cohen-Gadol and Dennis D. Spencer

✓ The temporal lobe is the most common site of partial epilepsy that is amenable to surgical therapy, and therefore ictal localization in this region is important. The authors describe the application of an anteromedial subdural strip electrode for the evaluation of epilepsy originating from the medial temporal lobe. This strip is advanced around the temporal pole and underneath the lesser wing of the sphenoid bone as it follows the medial temporal lobe contour. The advantages of this method of placement are the consistent path and reliable final position of the strip along the medial basal temporal lobe surface. This method allows adequate coverage of the parahippocampal gyrus along its long axis extending posterior to the level of the collicular plate. This technique has been used with no complications during intracranial monitoring of more than 100 patients with presumed temporal lobe epilepsy.