Imagined and actual limb selection: a test of preference.

Imagined and actual motor performance were compared to determine what factor(s) drive limb selection for programming movements in contralateral hemispace. Forty right-handed blindfolded subjects were asked to 'reach' via auditory stimulus for a small object placed at multiple locations in hemispace. Two conditions were included: arms uncrossed and arms crossed. With the uncrossed condition, responses were similar. With arms crossed, subjects had the choice of keeping the limbs crossed, reacting to proximity, or uncrossing the arms to reach ipsilaterally. In this condition subjects 'imagined' that they would maintain the crossedposition and reach with the hand closest to the stimulus in both right and left hemispace. However, during 'actual' reaching, responses differed. For left-field stimuli, participants kept the arms crossed, but in response to right-field stimuli, subjects preferred to uncross the limbs in order to reach with the dominant hand. These findings suggest that while motor dominance is the primary factor in limb choice for action in ipsilateral hemispace, it appears that object proximity drives limb selection for reaching in contralateral hemispace.

What determines choice of limb for unimanual reaching movements?

Currently, relatively little is known about what drives the choice of limb for goal-oriented reaching. Traditionally, the explanation has been tied predominately to motor dominance as manifested in handedness. This article offers data and an argument suggesting that handedness can be modified by attentional (spatial) information. Although motor dominance may be the controlling factor in the programming and execution of reaching movements at the midline and hemispace ipsilateral (same side) to the dominant limb, attentional information alters the programming of movements in what would be contralateral space. The general trend of behavior is characterized by reaching on the same side as the stimulus, in ipsilateral fashion, a phenomenon explained by kinesthetic efficiency and hemispheric bias.

Attentional effects on reaching in hemispace.

Previous evidence notes that attentional information in the form of visually guided stimuli can override motor dominance when programming reaching-to-grasp movements in contralateral hemispace. The present experiment verified these effects for 135 university students, using an auditory stimulus, and the pattern of behavior in the two modalities was quite similar.

Surgical treatment strategies in ischemic stroke.

Although the most dramatic recent advances in the treatment of stroke have been medical in nature, there still remains a role for surgery in selected patients with cerebrovascular ischemic disorders. Direct revascularization procedures, including carotid endarterectomy and extracranial-intracranial bypass, remain important tools for the vascular neurosurgeon. Lastly, decompressive hemicraniectomy is being increasingly performed in patients with massive nondominant infarcts, as a means of salvaging individuals who otherwise would succumb to herniation. This article addresses the current indications, techniques, and results of the aforementioned techniques for the surgical treatment of ischemic stroke.

Catastrophic subarachnoid hemorrhage resulting from ruptured vertebrobasilar dolichoectasia: case report.

OBJECTIVE AND IMPORTANCE: Two patients with vertebrobasilar dolichoectasia sustained massive fatal subarachnoid hemorrhage from rupture of the basilar artery wall. Hemorrhage from this entity is not widely known to occur during its natural history and may be exacerbated by systemic anticoagulation. CLINICAL PRESENTATION: Two patients presented with ischemic events of the brain stem, which were attributed to vertebrobasilar dolichoectasia. The diagnosis was made on the basis of computed tomography and subsequent angiography. INTERVENTION: Both patients were treated with systemic anticoagulation with heparin and subsequently experienced massive fatal subarachnoid hemorrhage. Autopsy results confirmed the cause of hemorrhage to be frank rupture of the basilar artery wall. CONCLUSION: Vertebrobasilar dolichoectasia is a formidable structural entity afflicting the posterior circulation, which is generally thought to cause symptoms as a result of either compression of the adjacent brain stem and/or cranial nerves or ischemic events caused by thrombosis and perforator occlusion. Our experience with these two patients indicates that some lesions can hemorrhage, which is a factor that must be weighed when considering treatment alternatives.

Attentional stimuli and programming hand selection: a developmental perspective.

This experiment examined the use of attentional stimuli for reaching in hemispace by strong right-dominant adults and children. Driving the hypothesis was the notion that developmental factors associated with use of attentional information may affect the programming of reaching movements in hemispace. Although the general pattern of responses was similar for both samples, children did not use attentional cues to program reaching movements in contralateral hemispace as effectively as adults. This result suggests that motor dominance and perhaps other factors were pivotal in motor programming for children. One possible explanation for the general behavior observed underlies an attentional hemispheric bias for a tendency to use the hand that is on the same side as the stimulus.

Initial experience with endoscopic carpal tunnel release surgery.

A retrospective analysis of patients who underwent endoscopic carpal tunnel release (ECTR) surgery at the authors' institution during the past 18 months was performed. Twenty-six ECTR surgeries were performed in 24 patients. Eighty-seven percent of patients experienced significant improvement or resolution of their symptoms following ECTR. Of the patients in whom surgery failed, those who have undergone postoperative assessment of nerve conduction velocities have experienced improvement or normalization. Three patients (12.5 %) underwent ECTR after a previous open procedure in the contralateral hand; all three patients preferred the ECTR procedure. One significant complication, a lacerated ulnar artery, was noted. It is concluded that ECTR is a promising technique that appears to have similar efficacy to open CTR and has the potential to be a superior technique.

A lateralized comparison of handedness and object proximity.

This study was motivated by the emerging hypothesis that right-handers are more strongly lateralized and perform better on various aspects of functional asymmetry than do left-handers. Right- and left-handers were observed for hand selection responses to a unimanual task of reaching for a small cube in positions of right- and left hemispace, prompting hemispheric decision-making related to hand dominance and attentional (visuospatial) stimuli. As predicted, left-handers did not respond with their preferred limb as consistently across positions as did right-handers. Additional inspection of the task suggests that being lateralized may not be a disadvantage in this context, and that environmental influence may play a significant role in hand selection for a particular motor event.

Options for cerebral protection after penetrating head injury.

The medical management of secondary brain injury is entering a new era in which the fruits of labor in the laboratory are paying off in the form of legitimate agents for use in human trials. As more about pathophysiology of traumatic-ischemic brain injury becomes known, more effective means for pharmacologic intervention and neuronal salvage will emerge, and optimism is high that we are approaching an era that will witness improvements in functional survival that have been heretofore unwitnessed.

Enlarging subependymal cyst: case report.

A 1-month-old infant with a Dandy-Walker malformation underwent the placement of a ventriculoperitoneal shunt to treat progressive hydrocephalus. On the initial computed tomographic scan, a subependymal cystic lesion larger than 1 cm in diameter was noted in the head of the right caudate nucleus, which enlarged to 3 cm in diameter on follow-up imaging studies over the course of a year. Biopsies taken at the time of fenestration failed to show the presence of neoplasia. This appears to be the first reported case of a cyst of this nature to show progressive enlargement.

Complex technical methodologies and their applications in the surgery of intracranial meningiomas.

As neurosurgery moves into the twenty-first century, improved visualization/localization techniques, neuromonitoring, and advanced instrumentation will become standards of care for all intracranial procedures. This article has focused on current available technologies that can be used to facilitate operations on intracranial meningiomas. Preoperative anatomic localization with MR imaging, CT, MR angiography, and angiography are standard techniques. Preoperative functional assessments with MR imaging, magnetic source imaging, PET, and functional MR imaging are crucial to recognize and preserve eloquent adjacent cortex. Pathologic correlations with preoperative imaging (i.e., MR imaging) may help to predict the histopathology. Perioperative rehearsal of the operation can be performed. Intraoperative anatomic localization is important to minimize the craniotomy, dural opening, and passage through normal neural structures. An impressive array of new technologies are currently available, including real-time ultrasonography, frame-based stereotaxy (CT, MR imaging PET), frameless stereotaxy (acoustic localization, neuronavigators, real-time visualization), robotics, neuroendoscopy, and intraoperative dye administration. Increased understanding of the function and individual variability of the human cortex underscores the importance of intraoperative functional localization by electrocorticography and optical imaging. Continuous intraoperative neuromonitoring of sensory (SSEPs, BAERs, visual evoked potentials) and motor evoked potentials is now standard during many intracranial procedures. Complex adjunctive instrumentation, such as the ultrasonic aspirator and the laser, are part of the contemporary armamentarium for meningioma surgery. As we have stated in a previous article, "Developmental trends imply realization of three major directions of technical neurosurgery: (1) precise preoperative simulation, (2) minimization or avoidance of transcranial operative corridors, [and] (3) increased refinement of technical adjuvants--both physical and molecular." The end point of these technical advances is to improve precision and safety and will enhance the outcome in each surgical procedure so that one day we will be able to operate on patients with intracranial lesions with minimal morbidity.

A statistical analysis of factors related to symptomatic cerebral vasospasm.

A retrospective review of patients presenting to our institution with aneurysmal subarachnoid hemorrhage between 1980-1990 was accomplished. Eleven variables were examined as to their relationship to clinical vasospasm: age, sex, clinical grade, amount of subarachnoid blood on CT, aneurysm location, incidence of vasospasm, incidence of complications, use of calcium channel blockers, time to surgery, length of stay, and outcome. Data were analyzed with univariate and multivariate logistical regression methodology. By univariate analysis, age under 20, amount of subarachnoid hemorrhage, and clinical grade were associated with a higher risk of vasospasm. Using multivariate logistic regression, these factors, along with age under 35, were correlated as being predictive of clinical vasospasm. When all patients are grouped into either good or bad outcome, and a similar analysis is performed, only in the poor outcome group is the amount of subarachnoid hemorrhage and clinical grade correlated with vasospasm. This suggests that there is a group of patients with a predisposition to vasospasm that is independent of subarachnoid hemorrhage and clinical grade, and that these patients may have a more favorable outcome.

Isolated cerebral mucormycosis: case report and therapeutic considerations.

Cerebral mucormycosis (without associated involvement of and invasion from the nasal sinuses and turbinates) is an extremely rare opportunistic infection of the central nervous system. We report the case of an intravenous drug abuser (who was negative for the human immunodeficiency virus) who presented with hemiparesis on the right side, slurred speech, altered mental status, and an unsteady gait. Imaging studies revealed a large left-side basal ganglia lesion. A stereotactic biopsy obtained a tissue sample that revealed wide, nonseptated hyphal fragments with granulomatous inflammation. The patient was treated with 3 gm of amphotericin B during a 5-month period. The patient had no residual neurological dysfunction after treatment. Open surgical resection was not employed. This case suggests that stereotactic biopsy followed by long-term amphotericin B therapy, in lieu of open surgical resection, represents a viable treatment option for this rare disorder.

Hemangiopericytoma of the temporal bone presenting as a retroauricular mass.

An unusual case of a hemangiopericytoma arising from the temporal bone is presented. The patient was noted to have a postauricular mass and was neurologically asymptomatic. A preoperative magnetic resonance image and an angiogram revealed the tumor to be highly vascular. Preoperative embolization facilitated the surgical removal of the tumor by rendering it avascular. Current therapy consists of radical resection of the tumor with postoperative radiation therapy. Patients must be monitored carefully for local recurrence and systemic metastasis.

Cardiac performance enhancement from dobutamine in patients refractory to hypervolemic therapy for cerebral vasospasm.

The use of the beta-agonist dobutamine in combination with hypervolemic preload enhancement of cardiac performance was analyzed in 23 patients who failed to respond to traditional preload enhancement following aneurysmal subarachnoid hemorrhage. The patients ranged in age from 13 to 82 years, and three had a history of cardiac disease. Each patient underwent placement of a flow-directed balloon-tipped catheter and the following measurements were obtained during hyperdynamic therapy: pulmonary artery wedge pressure, central venous pressure, cardiac index, stroke volume index, total peripheral resistance, and left ventricular stroke work index (LVSWI). Mean baseline cardiac function was found to be within normal limits (LVSWI = 47.6 +/- 4.2 gm/min/sq m and cardiac index = 3.30 +/- 0.22 liter/min/sq m). After baseline measurements were recorded, 5% albumin was infused at 300 cc/hr and dobutamine was initiated at a rate of 5 to 10 micrograms/kg/hr. This hyperdynamic therapy with dobutamine in the presence of volume loading resulted in a 52% increase in cardiac index, a 15% increase in LVSWI, and a 21% decrease in total peripheral resistance. The clinical reversal of ischemic symptoms due to subarachnoid hemorrhage was evident in 18 (78%) of the 23 patients.

Spinal arachnoid cysts in the pediatric age group: an association with neural tube defects.

Between 1979 and 1991, spinal arachnoid cysts were found in 11 patients aged 19 months to 18 years (mean age 5 1/2 years). Of the 11 patients, six had a myelomeningocele and one diastematomyelia. The presenting symptoms included radicular pain (one patient), progressive weakness (three), increasing scoliosis (one), worsening spasticity (three), and recurrent urinary tract infections and progressive constipation (one). Two patients showed no symptoms from the spinal arachnoid cyst. The distribution of lesions was as follows: cervicomedullary (one patient), cervical (one), cervicothoracic (two), thoracic (four), lumbar (two), and sacral (one). Four of the 11 arachnoid cysts (all intradural) were located anterior to the spinal cord, three of which were in children with a myelomeningocele. Only two of the cysts were extradural; both were found in the lumbosacral region, and one was associated with diastematomyelia. Eight patients were treated with fenestration and/or resection of the cyst wall. Three patients with anterior cysts were treated with shunts, a cyst-to-pleural space shunt in two and a cyst-to-subarachnoid space shunt in one. All of the patients either improved or exhibited an arrest in the progression of their symptoms. Spinal arachnoid cysts are a treatable cause of progressive neurological deficits and, in this series, were frequently found in patients with neural tube defects.