Raif Cakmur

The spatial location of EEG electrodes: locating the best-fitting sphere relative to cortical anatomy

The location of the international 10-20 system electrode positions and 14 fiducial landmarks are described in cartesian coordinates (+/- 1.4 mm average accuracy). Six replications were obtained on 3 separate days from 4 normal subjects, who were compared to each other with a best-fit sphere algorithm. Test-retest reliability depended on the electrode position: the parasagittal electrodes were associated with greater measurement errors (maximum 7 mm) than midline locations. Location variability due to head shape was greatest in the temporal region, averaging 5 mm from the mean. For each subjects electrode locations a best-fitting sphere was determined (79-87 mm radius, 6% average error). A surface-fitting algorithm was used to transfer the electrode locations and best-fitting sphere to MR images of the brain and scalp. The center of the best-fitting sphere coincided with the floor of the third ventricle 5 mm anterior to the posterior commissure. The melding of EEG electrode location information with brain anatomy provides an empirical basis for associating hypothetical equivalent dipole locations with their anatomical substrates.

Treatment of Carpal Tunnel Syndrome with Nerve and Tendon Gliding Exercises

Akalin E, El Ö, Peker Ö, Şenocak Ö, Tamci Ş, Gülbahar S, Çakmur R, Öncel S: Treatment of carpal tunnel syndrome with nerve and tendon gliding exercises. Am J Phys Med Rehabil 2002;81:108–113. ObjectiveTo assess the effect of nerve and tendon gliding exercises in carpal tunnel syndrome. DesignThe study was a prospective, randomized, before-and-after treatment trial. A total of 28 patients with the diagnosis of carpal tunnel syndrome in 36 hands were randomly assigned to two groups. A custom made neutral volar wrist splint was given to group 1 and group 2. The patients were instructed to wear the splints all night and during the day as much as possible for 4 wk. The patients in group 2 were also instructed to perform series of nerve and tendon gliding exercises in addition to the splint treatment. Patients were evaluated with clinical parameters, a functional status scale, and a symptom severity scale. ResultsAt the end of treatment, statistically significant improvement was obtained in all parameters in both groups. The improvement in group 2 was slightly greater, but the difference between the groups was not significant, except for the lateral pinch strength value. Patient satisfaction was investigated during the follow-up period, ranging from 5 to 11 mo, with a mean of 8 mo. A total of 72% of the patients in group 1 and 93% of the patients in group 2 reported good or excellent results. The difference between the two groups was not statistically significant. ConclusionAlthough the results in group 2 were better than group 1, the difference was not statistically significant. Further investigations are required to establish the role of nerve and tendon gliding exercises in the treatment of carpal tunnel syndrome.

Comparison of preseptal and pretarsal injections of botulinum toxin in the treatment of blepharospasm and hemifacial spasm

Abstract Although the beneficial effect of subcutaneous injections of botulinum toxin type A (BTX-A) is well known in both blepharospasm and hemifacial spasm, the position of the injection sites around the orbicularis oculi may influence the effectiveness and side effects. Here we report results of preseptal and pretarsal BTX-A injections in 53 patients (25 blepharospasm and 28 hemifacial spasm) in whom we used both injection techniques successively. Pretarsal injections were used in 102 out of 186 treatments in blepharospasm group and in 84 out of 202 treatments in hemifacial spasm group. Pretarsal BTX-A treatment produced significantly higher response rate and longer duration of maximum response in both patient groups. This technique was also associated with a lower frequency of major side effects such as ptosis. We concluded that injections of BTX-A into the pretarsal, rather than the preseptal portion of the orbicularis oculi is more effective for treatment of involuntary eyelid closure due to contractions of this muscle.

The effects of rasagiline on cognitive deficits in Parkinson's disease patients without dementia: A randomized, double-blind, placebo-controlled, multicenter study

Cognitive impairment can occur at all stages of Parkinsons disease. Rasagiline is a selective monoamine oxidase type‐B inhibitor that enhances central dopaminergic transmission. Dopamine is thought to be involved in certain cognitive processes such as working memory. We assessed the effects of rasagiline on cognitive deficits in cognitively impaired, nondemented patients with Parkinsons disease. This was a randomized, double‐blind, placebo‐controlled prospective study. Patients with Parkinsons disease receiving stable dopaminergic treatment were assigned to receive rasagiline 1 mg/day or placebo for 3 months. Patients were eligible if they had impairment in 2 of 4 cognitive domains (attention, executive functions, memory, visuospatial functions) in the screening neuropsychological tests, yet did not fulfill criteria for Parkinsons disease dementia. Fifty‐five patients were randomized; 48 patients completed the study. Patients in the rasagiline group showed significant improvement in digit span–backward compared with the placebo group (P = .04), with trends favoring rasagiline in digit span total and digit‐ordering tests. Verbal fluency total score showed a significant difference in favor of rasagiline (P = .038), with trends favoring rasagiline in semantic fluency test and Stroop spontaneous corrections. The composite cognitive domain Z scores revealed a significant difference in favor of rasagiline compared with placebo in the attentional Z score (P < .005). There were no significant differences between the 2 groups in the other cognitive tests or cognitive domain Z scores. The monoamine oxidase type‐B inhibitor rasagiline may exert beneficial effects on certain aspects of attention and executive functions in nondemented patients with Parkinsons disease with cognitive impairment.

Comparison of cortical excitability in chronic migraine (transformed migraine) and migraine without aura

We studied the excitability of the motor cortex in patients with migraine without aura (MWOA) (n = 20) and with chronic migraine (CM) (n = 20) using transcranial magnetic stimulation (TMS). By using a 90-mm circular coil placed over the vertex and recording of the first dorsal interosseous muscle, we measured thresholds, latencies and amplitudes of motor evoked potentials and duration of cortical silent periods in patient groups and in controls (n = 20). No differences were found between groups for threshold, latency and amplitude values. However, the duration of the cortical silent period was longer in CM patients, being significantly different from both controls and MWOA. We suggest that either this difference in cortical excitability may develop during transformation from MWOA to CM or different pathophysiological mechanisms may play a role in these two headache syndromes.

Dermatomal and mixed nerve somatosensory evoked potentials in the diagnosis of neurogenic thoracic outlet syndrome

To evaluate the diagnostic utility of dermatomal and mixed nerve somatosensory evoked potentials (SEPs) in patients with thoracic outlet syndrome (TOS) and to compare their value with routine electrodiagnostic methods, we studied a group of 44 patients with neurogenic TOS and 30 healthy controls. In addition to bilateral median and ulnar SEPs, evoked potentials were recorded after stimulation of C6 and C8 dermatomes from the first and fifth digits, respectively. The patients were classified into 3 groups according to the nature of their clinical condition. The abnormality rate for both ulnar and C8 dermatomal SEPs was 100% in a small group of patients with severe neurological signs like atrophy. In groups of patients with lesser degrees of neurogenic damage, abnormality rates for ulnar and C8 dermatomal SEPs on affected limb(s) were 67 and 50%, respectively. Same abnormality rates were 25 and 18% in patients with only subjective symptoms. In patients with objective neurological signs, the major increase in sensitivity was with electromyography (EMG). Abnormalities of routine nerve conduction studies and F-wave latency were observed in patients with severe neurogenic damage. We concluded that the most useful tests in the diagnosis of neurogenic TOS are needle EMG and ulnar SEPs.

Intra-Operative Localization of Sensorimotor Cortex by Cortical Somatosensory Evoked Potentials: From Analysis of Waveforms to Dipole Source Modeling

SummaryIntra-operative localization of sensorimotor cortex is of increasing importance as neurosurgical techniques allow safe and accurate removal of lesions around the central sulcus. Although direct cortical recordings of somatosensory evoked potentials (SEPs) are known to be helpful for cortical localization, source localization models can provide more precise estimates than subjective visual analysis. In addition to intra-operative analysis of waveforms and amplitudes of SEPs to median nerve stimulation in 20 neurosurgical patients, we used a spatiotemporal dipole model to determine the location of the equivalent dipoles consistent with the cortical distribution of the SEPs. The early cortical SEPs were modeled by 2 equivalent dipoles located in the postcentral gyrus. The first dipole was primarily tangentially oriented and explained N20 and P20 peaks. The second dipole was primarily radially oriented and explained P25 activity. We found consistent localization of the first dipole in the postcentral gyrus, which was always located within 8 mm of the central sulcus, with an average distance of 3 mm. This finding provides an objective basis for using the SEP phase reversal method for cortical localization. We conclude that dipole source modeling of the cortical SEPs can be considered as an objective way of localizing the cortical hand sensory area.

Cortical silent period and motor evoked potentials in patients with multiple sclerosis

In order to determine the importance of central motor conduction time (CMCT) and silent period (SP) in patients with multiple sclerosis (MS), we enrolled this clinical and electrophysiological study. Additionally, we planned to compare the correlation between electrophysiological findings and clinical status. We examined 58 patients with definite MS and 31 controls. Patients were classified as relapsing-remitting (N: 37), secondary progressive (N: 21) groups. Eleven out of 58 patients with MS had no neurological findings (subclinical patients). We evaluated CMCT and the duration of SP. Prolonged CMCT latency was shown in 75.2% of patients. We observed SP abnormalities in 69% of patients. In subclinical patients, SP abnormalities (six of 11) were observed more common than CMCT (two of 11). The duration of SP was extremely prolonged in MS patients with cerebellar dysfunction. When the both electrophysiological parameters are taken into account, the abnormality ratio was determined as 89.7%. Our results indicate that CMCT and SP analysis are complementary tests in evaluating motor pathways of patients with MS. We observed a relationship between cerebellar dysfunction and SP prolongation. It is suggested that, SP can be applied in patients with pure cerebellar dysfunction and it can be a valuable test in subclinical cases with MS.

Coexistence of movement disorders and epilepsia partialis continua as the initial signs in probable creutzfeldt-jakob disease

Movement disorders and epilepsy rarely occur in the early stage of Creutzfeldt–Jakob disease (CJD) but have not been reported concurrently. We report on a 47‐year‐old patient with probable CJD who presented with generalized chorea and focal dystonia with myoclonic jerks on the right hand. Myoclonic jerks progressed to epilepsia partialis continua within 5 days of admission to the hospital. The diagnosis of our patient was compatible with probable CJD on the basis of clinical course, electroencephalogram, and diffusion‐weighted magnetic resonance imaging findings, and presence of 14‐3‐3 protein in cerebrospinal fluid. To our knowledge, this is the first report of a case developing both movement disorders and epilepsia partialis continua in the early stage of the disease.

Locating vep equivalent dipoles in magnetic resonance images

Pattern-reversal and diffuse flash visual evoked potentials (VEPs) were obtained from 4 normal adults. A spatiotemporal dipole model was used to determine the location of the hypothetical equivalent dipoles consistent with the scalp distribution of the VEPs. Equivalent dipoles representing ERG and VEP activity were placed within 3-D magnetic resonance images of the brain. Most of the localization error appeared to be due to inadequate sampling of the potential field in frontal and occipital areas by the 10-20 system of electrode placement. Locating electrophysiologic dipoles within magnetic resonance images of brain structure allows evaluation of dipole localization techniques.