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Biomedical subjects

Peter Kim Nelson

Publications and source records attributed to Peter Kim Nelson.

6 recordsLinked to original sources
PubMed2006

Degree of handedness and cerebral dominance.

OBJECTIVE: To examine the relationship between the degree of handedness and hemispheric language dominance in patients with epilepsy. METHODS: The authors examined the relationship between degree of handedness and hemispheric language dominance in 174 epilepsy surgery candidates using the intracarotid amobarbital procedure and results from a modified version of the Edinburgh Handedness Inventory. RESULTS: The incidence of atypical language dominance increased linearly with the degree of left-handedness, from 9% in strong right-handers (laterality quotient [LQ] = +100) to 46% in ambidextrous individuals and 69% in strong left-handers (LQ = -100). CONCLUSIONS: The incidence of atypical language dominance depends not only on the direction but also on the degree of handedness. In addition, direction of language dominance varies with hemisphere of seizure focus and degree of handedness. A familial history of sinistrality may have an additional effect on the likelihood of atypical dominance.

Adolescent↗
PubMed2006

Prediction of false-positive recognition errors during Wada testing.

False-positive (FP) errors during recognition memory testing often interfere with interpretation of Wada test results. This study examined which clinical and neuropsychological variables provide the best prediction of these errors. Fifty-six patients completed the Wada test and the California Verbal Learning Test (CVLT). Subjects with three or more FP errors on the recognition trials of the CVLT were nearly twice as likely to exhibit FP responding during the Wada test. Further analysis indicates that FP errors during the Wada test appear to be the primary result of a stable and liberal response-bias rather than a result of any other neurological or procedure-related factor.

Adult↗
PubMed2006

Perfusion and diffusion tensor imaging in a patient with locked-in syndrome after neurosurgical vascular bypass and endovascular embolization of a basilar artery aneurysm: case report.

OBJECTIVE AND IMPORTANCE: Locked-in syndrome is a state of preserved consciousness in the setting of quadriplegia, anarthria, and usually also includes lateral gaze palsy. It is most commonly associated with upper brainstem infarction variably sparing the third cranial nerve nucleus. There are likely many etiologies that contribute to this clinical syndrome. These are incompletely understood, and the syndrome remains a rare but devastating complication that can occur after neurosurgical and neurovascular interventions. Advanced magnetic resonance imaging techniques such as perfusion and diffusion tensor imaging may help to elucidate the mechanism behind locked-in syndrome. To the authors' knowledge, there are no reports in the literature of perfusion and diffusion tensor findings in patients with this syndrome. A postprocedural case of locked-in syndrome is described with abnormalities on perfusion and diffusion tensor imaging in the absence of any changes in conventional magnetic resonance imaging. CLINICAL PRESENTATION: A 57-year-old man who presented with acute onset headache, ataxia, and other nonspecific symptoms was found on imaging to have a giant fusiform basilar artery aneurysm. INTERVENTION: A saphenous vein graft bypass between the proximal right external carotid artery and P2 segment of the right posterior cerebral artery followed immediately by endovascular embolization of the aneurysm sac and distal left vertebral artery was performed. CONCLUSION: Postprocedural angiography demonstrated patency of the bypass graft, and diffusion weighted imaging showed no evidence for acute brainstem infarction. Nevertheless, despite technically successful procedures and the absence of abnormalities on conventional magnetic resonance imaging, the patient developed quadriplegia and anarthria and remained in a locked-in state until he expired. Abnormalities were, however, seen on both perfusion and diffusion tensor imaging, where hypoperfusion, increased mean diffusivity, and decreased fractional anisotropy were observed in the ventral brainstem. The findings suggested a disruption of pontine white matter tracts. Advanced imaging techniques may allow us to image important microstructural changes that were previously not discernable and assist in the evaluation of patients with complex neurological sequelae such as locked-in syndrome.

Basilar Artery↗
PubMed2003

Use of a wedged microcatheter for curative transarterial embolization of complex intracranial dural arteriovenous fistulas: indications, endovascular technique, and outcome in 21 patients.

OBJECT: The aim of this study was to describe the application of a novel transarterial approach to curative embolization of complex intracranial dural arteriovenous fistulas (DAVFs). This technique is particularly useful in patients harboring high-grade DAVFs with direct cortical venous drainage or for whom transvenous coil embolization is not possible because of limited sinus venous access to the fistula site due to thrombosis or stenotic changes. METHODS: Twenty-three DAVFs in 21 patients were treated using a transarterial N-butyl cyanoacrylate (NBCA) embolization technique with the aid of a wedged catheter. In all patients, definitive treatment involved two critical steps: 1) a microcatheter was wedged within a feeding artery, establishing flow-arrest conditions within the catheterized vessel distal to the microcatheter tip; and 2) NBCA was injected under these resultant flow-arrest conditions across the pathological arteriovenous connection and into the immediate draining venous apparatus, definitively occluding the fistula. Patient data were collected in a retrospective manner by reviewing office and inpatient charts and embolization reports, and by directly analyzing all procedural and diagnostic angiograms. Eight patients presented with the principal complaint of tinnitus/bruit, five with intracranial hemorrhage, four with cavrnous sinus syndrome, and one each with seizures, ataxia, visual field loss, and hiccups. The parent (recipient) venous structure of the DAVFs in this study included 11 leptomeningeal veins, eight transverse/sigmoid sinuses, three cavernous sinuses, and one sphenoparietal sinus. The NBCA permeated the arteriovenous shunt, perifistulous network, and proximal draining vein in all DAVFs. Occlusion was confirmed on postembolization angiography studies. No complication occurred in any patient in this series. There has been no recurrence during a mean follow up of 18.7 months (range 2-46 months). CONCLUSIONS: Transarterial NBCA embolization with the aid of a wedged catheter in flow-arrest conditions is a safe and an effective treatment for intracranial DAVFs.

Adolescent↗
PubMedDate not supplied

Preoperative assessment of intracranial tumors with perfusion MR and a volumetric interpolated examination: a comparative study with DSA.

BACKGROUND AND PURPOSE: In evaluating intracranial tumors, a safe low-cost alternative that provides information similar to that of digital subtraction angiography (DSA) may be of interest. Our purpose was to determine the utility and limitations of a combined MR protocol in assessing (neo-) vascularity in intracranial tumors and their relation to adjacent vessels and to compare the results with those of DSA. METHODS: Twenty-two consecutive patients with an intracranial tumor who underwent preoperative stereoscopic DSA were examined with contrast-enhanced dynamic T2*-weighted perfusion MR imaging followed by a T1-weighted three-dimensional (3D) MR study (volumetric interpolated brain examination [VIBE]). The maximum relative cerebral blood volume (rCBV) of the tumor was compared with tumor vascularity at DSA. Critical vessel structures were defined in each patient, and VIBE images of these structures were compared with DSA findings. For full exploitation of the 3D data sets, maximum-intensity projection algorithms reconstructed in real time with any desired volume and orientation were used. RESULTS: Tumor blush scores at DSA were significantly correlated with the rCBV measurements (r = 0.75; P <.01, Spearman rank correlation coefficient). In 17 (77%) patients, VIBE provided all relevant information about the venous system, whereas information about critical arteries were partial in 50% of the cases and not relevant in the other 50%. CONCLUSION: A fast imaging protocol consisting of perfusion MR imaging and a volumetric MR acquisition provides some of the information about tumor (neo-) vascularity and adjacent vascular anatomy that can be obtained with conventional angiography. However, the MR protocol provides insufficient visualization of distal cerebral arteries.

Adult↗