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Cormac O. Maher and Fraser C. Henderson

Object. Hypertrophy of the superior facet of the inferior vertebra, resulting in a compression of the nerve root at the lateral foraminal exit, is a recognized cause of radicular symptoms, particularly in patients in whom previous lumbar spine surgery has failed. The lesion-specific presenting symptoms, imaging findings, and surgical treatment of this lesion, however, have received little attention. The authors prospectively studied a series of eight consecutive patients, in whom a diagnosis of lumbar stenosis at the lateral foraminal exit had been made, to elucidate the common presenting signs and symptoms of this disorder, as well as to evaluate the success of the operative treatment.

Methods. The eight patients were selected from a group of 250 consecutive patients who presented to a tertiary-care hospital and in whom a diagnosis of long-standing lumbar radiculopathy had been made. In all cases the diagnosis was confirmed by imaging studies and by intraoperative findings. The authors performed decompressive procedures on the nerve root via a medial facet-sparing approach.

Conclusions. The authors conclude that this lesion presents with characteristic physical findings and on imaging studies that distinguish it from other causes of radiculopathy, and they propose a lesion-specific, facet-sparing surgical technique that has yielded excellent results.

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Cormac O. Maher, Fredric B. Meyer and Bahram Mokri

Spontaneous spinal cerebrospinal fluid (CSF) leaks are an increasingly recognized cause of intracranial hypotension. In this report the authors review the indications for surgery, surgical techniques, and surgery-related outcomes for these lesions. The major presenting symptoms include postural headaches, nausea, vomiting, and diplopia. Often, there is no history of traumatic injury. The most common cranial magnetic resonance (MR) imaging features include pachymeningeal gadolinium enhancement and sagging of the brain. On spinal MR images, diverticula are frequently noted. In cases in which symptoms are severe and refractory to less invasive measures, surgical intervention is indicated. Tears in the dura or leaking diverticula that are identified as the sources of the CSF leak often can be ligated or repaired. When a source of CSF egress is not found intraoperatively, packing the epidural space with blood-soaked Gelfoam or muscle at the appropriate level can lead to relief of symptoms. Occasionally the dural defect is large, irregular, or has attenuated borders that may not be possible to repair with sutures. These may be repaired by packing the defect with muscle or blood-soaked Gelfoam. Indications for and outcomes of surgery in patients with this condition will become more defined as surgeons gain experience with these procedures.

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Cormac O. Maher, James A. Garrity and Fredric B. Meyer

Object

Ventriculoperitoneal (VP) shunts have not been widely used for idiopathic intracranial hypertension (IIH) because of the difficulty of placing a shunt into normal or small-sized ventricles. The authors report their experience with stereotactic placement of VP shunts for IIH.

Methods

The authors reviewed the clinical records of all patients in whom stereotaxis was used to guide the placement of a VP shunt for IIH at their institution. All shunts were placed using stereotactic guidance to target the frontal horn of the lateral ventricle. Patients were contacted at a mean postoperative interval of 15.1 months. No patients were lost to follow up.

The authors identified 13 patients who underwent placement of a stereotactically guided VP shunt for IIH over a 6-year period. A trial of either acetazolamide or steroid therapy had failed in all patients. Prior surgical treatments included optic nerve sheath fenestrations in seven patients and cerebrospinal fluid diversionary procedures, other than stereotactic VP shunt procedures, in nine patients. Twelve patients reported excellent or good durable symptomatic relief at the time of follow up. No patient suffered progression of visual deficits. Four patients experienced persistent headaches following the procedure. Three patients required a revision of the VP shunt for technical failure.

Conclusions

Stereotactically guided VP shunt placement is an effective and durable treatment option in many cases of IIH that are refractory to more traditional medical and surgical approaches.

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Jonathan A. Friedman, Mark A. Pichelmann, David G. Piepgras, John L. D. Atkinson, Cormac O. Maher, Fredric B. Meyer and Kristine K. Hansen

Object. Anterior choroidal artery (AChA) aneurysms account for 4% of all intracranial aneurysms. The surgical approach is similar to that for other supraclinoid carotid artery lesions, but surgery may involve a higher risk of debilitating ischemic complications because of the critical territory supplied by the AChA.

Methods. Between 1968 and 1999, 51 AChA aneurysms in 50 patients were treated using craniotomy and clipping at the Mayo Clinic. There were 22 men (44%) and 28 women (56%) whose average age was 53 years (range 27–79 years). Twenty-four AChA aneurysms (47%) had hemorrhaged; nine patients (18%) had subarachnoid hemorrhage from another aneurysm. Three AChA aneurysms (6%) were associated with symptoms other than rupture. Forty-one patients (82%) achieved a Glasgow Outcome Scale (GOS) score of 4 or 5 at long-term follow up. The surgical mortality rate was 4%, and major surgical morbidity (GOS ≤ 3) was 10%. Eight patients (16%) had clinically and computerized tomography—demonstrated AChA territory infarcts. Five of these strokes manifested in a delayed fashion 6 to 36 hours after the operation, and progressed from mild to complete deficit over hours. In 41 patients the aneurysm arose from the internal carotid artery adjacent to the AChA, and in nine patients the aneurysm arose directly from the origin of the AChA itself; four of these nine patients had postoperative infarction.

Conclusions. Surgical treatment of AChA aneurysms involves a significant risk of debilitating ischemic complications. Most postoperative strokes occur in a delayed fashion, offering a potential therapeutic window. Patients with aneurysms arising from the AChA itself have an extremely high risk for postoperative stroke.

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Jonathan A. Friedman, Fredric B. Meyer, Douglas A. Nichols, Robert J. Coffey, L. Nelson Hopkins, Cormac O. Maher, Irene D. Meissner and Bruce E. Pollock

✓ The authors report the case of a man who suffered from progressive, disseminated posttraumatic dural arteriovenous fistulas (DAVFs) resulting in death, despite aggressive endovascular, surgical, and radiosurgical treatment.

This 31-year-old man was struck on the head while playing basketball. Two weeks later a soft, pulsatile mass developed at his vertex, and the man began to experience pulsatile tinnitus and progressive headaches. Magnetic resonance imaging and subsequent angiography revealed multiple AVFs in the scalp, calvaria, and dura, with drainage into the superior sagittal sinus. The patient was treated initially with transarterial embolization in five stages, followed by vertex craniotomy and surgical resection of the AVFs. However, multiple additional DAVFs developed over the bilateral convexities, the falx, and the tentorium. Subsequent treatment entailed 15 stages of transarterial embolization; seven stages of transvenous embolization, including complete occlusion of the sagittal sinus and partial occlusion of the straight sinus; three stages of stereotactic radiosurgery; and a second craniotomy with aggressive disconnection of the DAVFs. Unfortunately, the fistulas continued to progress, resulting in diffuse venous hypertension, multiple intracerebral hemorrhages in both hemispheres, and, ultimately, death nearly 5 years after the initial trauma.

Endovascular, surgical, and radiosurgical treatments are successful in curing most patients with DAVFs. The failure of multimodal therapy and the fulminant progression and disseminated nature of this patient's disease are unique.

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Cormac O. Maher, Robert J. Spinner, Caterina Giannini, Bernd W. Scheithauer and Brian A. Crum

✓ The authors report the findings of a neuromuscular choristoma of the sciatic nerve in an otherwise healthy 18-year-old man who presented with sensorimotor symptoms and deformities of the right leg and foot. Only a few cases of this rare tumor, also known as “neuromuscular hamartoma” or “benign triton tumor,” have been reported in the surgical literature. The authors discuss the clinical presentation, radiological findings, pathological diagnosis, and surgical rationale for this case and review the associated literature.

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Cormac O. Maher, Nicholas M. Wetjen, Jonathan A. Friedman and Fredric B. Meyer

Object. Many surgeons inject a local anesthetic agent into the carotid sinus before carotid endarterectomy in an attempt to ameliorate perioperative hemodynamic instability. The purpose of this study is to analyze the effect of carotid sinus injection with lidocaine on perioperative hemodynamics and complications.

Methods. The authors prospectively studied 92 patients in whom 100 consecutive carotid endarterectomies were performed by a single surgeon (eight procedures were bilateral). Patients were randomly assigned to one of two groups, in which either 0.5 ml of 1% lidocaine was injected into the carotid sinus nerve or no injection of lidocaine was administered before the arteriotomy. All patients were treated postoperatively according to a standard endarterectomy protocol. There were no significant differences between the two groups in the incidence of hypertension, hypotension, or the use of vasoactive medications in the operating room following restoration of carotid artery (CA) blood flow, in the recovery room, or in the intensive care unit.

Conclusions. Injection of lidocaine into the carotid sinus at the time of endarterectomy is not associated with a significant improvement in any hemodynamic factor, from the time of restoration of CA blood flow to postoperative Day 1.

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Cormac O. Maher, John L. D. Atkinson and John I. Lane

✓ The authors report on an arteriovenous malformation (AVM) within the trigeminal nerve in an otherwise healthy 76-year-old man who presented with the sudden onset of headache and ataxia. The AVM was totally resected via a lateral sub-occipital approach to the cerebellopontine angle. Dural arteriovenous fistulas and AVMs of the dorsal root entry zone and adjacent brainstem that compress the trigeminal nerve have been previously described. To the authors' knowledge, this is the first reported case of an angiographically, surgically, and pathologically proven AVM arising from within the trigeminal nerve itself.

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Cormac O. Maher, Robert E. Anderson, Heidi S. Martin, Robyn L. McClelland and Fredric B. Meyer

Object. The effects of interleukin (IL)-1β on the cerebral vasculature are complex and incompletely understood. Many pathophysiological states in which inflammatory cascades have been implicated also have varying degrees of cerebral hypoperfusion. The purpose of this investigation was to examine the long-term effects of this proinflammatory cytokine and its antagonist on cerebral blood flow (CBF) following global cerebral hypoperfusion.

Methods. Sprague—Dawley rats were randomly assigned to 12 groups and given continuous intracerebroventricular (ICV) infusions of IL-1β, the IL-1 receptor antagonist (IL-1ra), or saline vehicle (control). Global cerebral hypoperfusion was produced by occlusion of both carotid arteries and one vertebral artery. Cerebral blood flow was measured at baseline and again after initiation of the infusions by performing a 133Xe clearance study.

Prolonged ICV administration of IL-1β resulted in a significant decrease in CBF compared with that in controls. Prolonged administration of the antagonist IL-1ra resulted in significant increases in CBF compared with that in both IL-1β—treated animals and controls.

Conclusions. This experiment demonstrates that long-term treatment with the proinflammatory cytokine IL-1β adversely affects CBF.

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Cormac O. Maher, Robert E. Anderson, Robyn L. McClelland and Michael J. Link

Object. The authors evaluated a new non—cross-linked, propylene oxide—treated, acellular collagen matrix for use as a dural substitute in rabbits. They then compared this material to a commonly used dural substitute as well as to native dura mater used during primary closure.

Methods. Forty-six rabbits were randomly assigned to eight groups of five or six rabbits each. These groups differed according to the type of closure material that was used during surgery (native dura, control dural substitute, or experimental dural substitute) and the duration of convalescence. At the end of the experiment, the tightness of the duraplasty was assessed in each live rabbit by continuous infusion of fluid into the cisterna magna until leakage was detected. The animals were killed and each specimen was sectioned and studied histologically. The authors found that the experimental dural substitute was safe in animals for this application, that it held sutures well, and that a watertight closure was usually achieved. There were fewer adhesions between the experimental material and neural tissue was less likely to adhere to the cranium than the control graft. Histological examination showed that the experimental material had slightly more spindle cells and vascularity than the control graft.

Conclusions. The experimental graft material has several features that make it an attractive candidate for use as a dural substitute.