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Localization of human sensorimotor cortex during surgery by cortical surface recording of somatosensory evoked potentials

Charles C. Wood, Dennis D. Spencer, Truett Allison, Gregory McCarthy, Peter D. Williamson, and William R. Goff

✓ The traditional means of localizing sensorimotor cortex during surgery is Penfield's procedure of mapping sensory and motor responses elicited by electrical stimulation of the cortical surface. This procedure can accurately localize sensorimotor cortex but is time-consuming and best carried out in awake, cooperative patients. An alternative localization procedure is presented that involves cortical surface recordings of somatosensory evoked potentials (SEP's), providing accurate and rapid localization in patients under either local or general anesthesia.

The morphology and amplitude of median nerve SEP's recorded from the cortical surface varied systematically as a function of spatial location relative to the sensorimotor hand representation area. These results were validated in 18 patients operated on under local anesthesia in whom the sensorimotor cortex was independently localized by electrical stimulation mapping; the two procedures were in agreement in all cases. Similar SEP results were demonstrated in an additional 27 patients operated on under general anesthesia without electrical stimulation mapping.

The following three spatial relationships between SEP's and the anatomy of the sensorimotor cortex permit rapid and accurate localization of the sensorimotor hand area: 1) SEP's with approximately mirror-image waveforms are recorded at electrode sites in the hand area on opposite sides of the central sulcus (P20–N30 precentrally (for consistency) and N20–P30 postcentrally); 2) the P25–N35 is recorded from the postcentral gyrus as well as a small region of the precentral gyrus in the immediate vicinity of the central sulcus: this waveform is largest on the postcentral gyrus about 1 cm medial to the focus of the 20- and 30-msec potentials; and 3) regardless of component identification, maximum SEP amplitudes are recorded from the hand representation area on the precentral and postcentral gyri.

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Robotic image-guided depth electrode implantation in the evaluation of medically intractable epilepsy

Technical note

William J. Spire, Barbara C. Jobst, Vijay M. Thadani, Peter D. Williamson, Terrance M. Darcey, and David W. Roberts

Object

The authors describe their experience with a technique for robotic implantation of depth electrodes in patients concurrently undergoing craniotomy and placement of subdural monitoring electrodes for the evaluation of intractable epilepsy.

Methods

Patients included in this study underwent evaluation in the Dartmouth Surgical Epilepsy Program and were recommended for invasive seizure monitoring with depth electrodes between 2006 and the present. In all cases an image-guided robotic system was used during craniotomy for concurrent subdural grid electrode placement. A total of 7 electrodes were placed in 4 patients within the time period.

Results

Three of 4 patients had successful localization of seizure onset, and 2 underwent subsequent resection. Of the patients who underwent resection, 1 is now seizure free, and the second has only auras. There was 1 complication after subpial grid placement but no complications related to the depth electrodes.

Conclusions

Robotic image-guided placement of depth electrodes with concurrent craniotomy is feasible, and the technique is safe, accurate, and efficient.

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Electrophysiological Localization of the Human Sensorimotor Cortex

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The many roles of microRNAs in brain tumor biology

Jay D. Turner, Richard Williamson, Kaith K. Almefty, Peter Nakaji, Randall Porter, Victor Tse, and M. Yashar S. Kalani

MicroRNAs (miRNAs) are now recognized as the primary RNAs involved in the purposeful silencing of the cell's own message. In addition to the established role of miRNAs as developmental regulators of normal cellular function, they have recently been shown to be important players in pathological states such as cancer. The authors review the literature on the role of miRNAs in the formation and propagation of gliomas and medulloblastomas, highlighting the potential of these molecules and their inhibitors as therapeutics.

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The relationship between ruptured aneurysm location, subarachnoid hemorrhage clot thickness, and incidence of radiographic or symptomatic vasospasm in patients enrolled in a prospective randomized controlled trial

Clinical article

Adib A. Abla, David A. Wilson, Richard W. Williamson, Peter Nakaji, Cameron G. McDougall, Joseph M. Zabramski, Felipe C. Albuquerque, and Robert F. Spetzler

Object

Cerebral vasospasm following subarachnoid hemorrhage (SAH) causes significant morbidity in a delayed fashion. The authors recently published a new scale that grades the maximum thickness of SAH on axial CT and is predictive of vasospasm incidence. In this study, the authors further investigate whether different aneurysm locations result in different SAH clot burdens and whether any concurrent differences in ruptured aneurysm location and maximum SAH clot burden affect vasospasm incidence.

Methods

Two hundred fifty patients who were part of a prospective randomized controlled trial were reviewed. Most outcome and demographic variables were included as part of the prospective randomized controlled trial. Additional variables were also collected at a later time, including vasospasm data and maximum clot thickness.

Results

Aneurysms were categorized into 1 of 6 groups: intradural internal carotid artery aneurysms, vertebral artery (VA) aneurysms (including the posterior inferior cerebellar artery), basilar trunk or basilar apex aneurysms, middle cerebral artery aneurysms, pericallosal aneurysms, and anterior communicating artery aneurysms. Twenty-nine patients with nonaneurysmal SAH were excluded. Patients with pericallosal aneurysms had the least average maximum clot burden (5.3 mm), compared with 6.4 mm for the group overall, but had the highest rate of symptomatic vasospasm (56% vs 22% overall, OR 4.9, RR 2.7, p = 0.026). Symptomatic vasospasm occurrence was tallied in patients with clinical deterioration attributable to delayed cerebral ischemia. There were no significant differences in maximum clot thickness between aneurysm sites. Middle cerebral artery aneurysms resulted in the thickest mean maximum clot (7.1 mm) but rates of symptomatic and radiographic vasospasm in this group were statistically no different compared with the overall group. Vertebral artery aneurysms had the worst 1-year modified Rankin scale (mRS) scores (3.0 vs 1.9 overall, respectively; p = 0.0249). A 1-year mRS score of 0–2 (good outcome) was found in 72% of patients overall, but in only 50% of those with pericallosal and VA aneurysms, and in 56% of those with basilar artery aneurysms (p = 0.0044). Patients with stroke from vasospasm had higher mean clot thickness (9.71 vs 6.15 mm, p = 0.004).

Conclusions

The location of a ruptured aneurysm minimally affects the maximum thickness of the SAH clot but is predictive of symptomatic vasospasm or clinical deterioration from delayed cerebral ischemia in pericallosal aneurysms. The worst 1-year mRS outcomes in this cohort of patients were noted in those with posterior circulation aneurysms or pericallosal artery aneurysms. Patients experiencing stroke had higher mean clot burden.

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Intradural cauda equina Candida abscess presenting with hydrocephalus: case report

Davis P. Argersinger, Vitaliy P. Natkha, Matthew J. Shepard, Alissa A. Thomas, Andrew J. Oler, Peter R. Williamson, Prashant Chittiboina, and John D. Heiss

Central nervous system (CNS) candida infections are often associated with a poor prognosis. Typically, CNS candidiasis presents as meningitis or microabscesses. Here, the authors report a patient with a challenging presentation of a CNS Candida infection as a discrete, large cauda equina abscess. The patient initially presented with ventriculomegaly due to fourth ventricular outflow obstruction and a cauda equina mass. The patient was treated with a ventriculoperitoneal shunt and underwent a lumbar laminectomy for exploration of the lumbar lesion. An intradural abscess was encountered during surgery. Fungal wet mount revealed fungal elements and polymerase chain reaction confirmed the presence of Candida albicans. The patient did not have any known predisposition to fungal infections; therefore, the authors performed whole-exome sequencing using peripheral blood mononuclear cell DNA. They found heterozygous missense variants in the following genes: colony-stimulating factor 2 (CSF2) and Ras protein-specific guanine nucleotide-releasing factor 1 (RASGRF1)—genes that have been specifically associated with protection from CNS candidiasis via caspase recruitment domain-containing protein 9 (CARD9) signaling, and phospholipase C gamma 2 (PLCG2)—a lectin receptor involved in candidiasis. The authors’ experience suggests that C. albicans can present as a cauda equina abscess. Hydrocephalus, a result of diffuse arachnoiditis, is a potential complication from intradural fungal abscesses.

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Long-term seizure, cognitive, and psychiatric outcome following trans–middle temporal gyrus amygdalohippocampectomy and standard temporal lobectomy

Clinical article

Krzysztof A. Bujarski, Fuyuki Hirashima, David W. Roberts, Barbara C. Jobst, Karen L. Gilbert, Robert M. Roth, Laura A. Flashman, Brenna C. McDonald, Andrew J. Saykin, Rod C. Scott, Eric Dinnerstein, Julie Preston, Peter D. Williamson, and Vijay M. Thadani

Object

Previous comparisons of standard temporal lobectomy (STL) and selective amygdalohippocampectomy (SelAH) have been limited by inadequate long-term follow-up, variable definitions of favorable outcome, and inadequate consideration of psychiatric comorbidities.

Methods

The authors performed a retrospective analysis of seizure, cognitive, and psychiatric outcomes in a noncontemporaneous cohort of 69 patients with unilateral refractory temporal lobe epilepsy and MRI evidence of mesial temporal sclerosis after either an STL or an SelAH and examined seizure, cognitive, and psychiatric outcomes.

Results

The mean duration of follow-up for STL was 9.7 years (range 1–18 years), and for trans–middle temporal gyrus SelAH (mtg-SelAH) it was 6.85 years (range 1–15 years). There was no significant difference in seizure outcome when “favorable” was defined as time to loss of Engel Class I or II status; better seizure outcome was seen in the STL group when “favorable” was defined as time to loss of Engel Class IA status (p = 0.034). Further analysis revealed a higher occurrence of seizures solely during attempted medication withdrawal in the mtg-SelAH group than in the STL group (p = 0.016). The authors found no significant difference in the effect of surgery type on any cognitive and most psychiatric variables. Standard temporal lobectomy was associated with significantly higher scores on assessment of postsurgical paranoia (p = 0.048).

Conclusions

Overall, few differences in seizure, cognitive, and psychiatric outcome were found between STL and mtg-SelAH on long-term follow-up. Longer exposure to medication side effects after mtg-SelAH may adversely affect quality of life but is unlikely to cause additional functional impairment. In patients with high levels of presurgical psychiatric disease, mtg-SelAH may be the preferred surgery type.

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Natural history of adult spinal deformity: how do patients with suboptimal surgical outcomes fare relative to nonoperative counterparts?

Peter G. Passias, Rachel Joujon-Roche, Jamshaid M. Mir, Tyler K. Williamson, Peter S. Tretiakov, Bailey Imbo, Oscar Krol, Lara Passfall, Salman Ahmad, Jordan Lebovic, Stephane Owusu-Sarpong, Tomi Lanre-Amos, Themistocles Protopsaltis, Renaud Lafage, Virginie Lafage, Paul Park, Dean Chou, Praveen V. Mummaneni, Kai-Ming G. Fu, Khoi D. Than, Justin S. Smith, M. Burhan Janjua, Andrew J. Schoenfeld, Bassel G. Diebo, and Shaleen Vira

OBJECTIVE

Management of adult spinal deformity (ASD) has increasingly favored operative intervention; however, the incidence of complications and reoperations is high, and patients may fail to achieve idealized postsurgical results. This study compared health-related quality of life (HRQOL) metrics between patients with suboptimal surgical outcomes and those who underwent nonoperative management as a proxy for the natural history (NH) of ASD.

METHODS

ASD patients with 2-year data were included. Patients who were offered surgery but declined were considered nonoperative (i.e., NH) patients. Operative patients with suboptimal outcome (SOp)—defined as any reoperation, major complication, or ≥ 2 severe Scoliosis Research Society (SRS)–Schwab modifiers at follow-up—were selected for comparison. Propensity score matching (PSM) on the basis of baseline age, deformity, SRS-22 Total, and Charlson Comorbidity Index score was used to match the groups. ANCOVA and stepwise logistic regression analysis were used to assess outcomes between groups at 2 years.

RESULTS

In total, 441 patients were included (267 SOp and 174 NH patients). After PSM, 142 patients remained (71 SOp 71 and 71 NH patients). At baseline, the SOp and NH groups had similar demographic characteristics, HRQOL, and deformity (all p > 0.05). At 2 years, ANCOVA determined that NH patients had worse deformity as measured with sagittal vertical axis (36.7 mm vs 21.3 mm, p = 0.025), mismatch between pelvic incidence and lumbar lordosis (11.9° vs 2.9°, p < 0.001), and pelvic tilt (PT) (23.1° vs 20.7°, p = 0.019). The adjusted regression analysis found that SOp patients had higher odds of reaching the minimal clinically important differences in Oswestry Disability Index score (OR [95% CI] 4.5 [1.7–11.5], p = 0.002), SRS-22 Activity (OR [95% CI] 3.2 [1.5–6.8], p = 0.002), SRS-22 Pain (OR [95% CI] 2.8 [1.4–5.9], p = 0.005), and SRS-22 Total (OR [95% CI] 11.0 [3.5–34.4], p < 0.001).

CONCLUSIONS

Operative patients with SOp still experience greater improvements in deformity and HRQOL relative to the progressive radiographic and functional deterioration associated with the NH of ASD. The NH of nonoperative management should be accounted for when weighing the risks and benefits of operative intervention for ASD.

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Oral Presentations 2015 AANS Annual Scientific Meeting Washington, DC • May 2–6, 2015

Published online August 1, 2015; DOI: 10.3171/2015.8.JNS.AANS2015abstracts

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Abstracts of the 2017 AANS/CNS Joint Section on Disorders of the Spine and Peripheral Nerves Las Vegas, Nevada • March 8–11, 2017