Reduction of negative afterimage duration in Parkinson's disease patients: a possible role for dopaminergic deficiency in the retinal Interplexiform cell layer

Dopaminergic deficiency may affect Parkinson's disease patients (PD) in the central as well as the peripheral tissues. In the retina, the neuromodulatory role of the dopaminergic Interplexiform cell layer (IP) plays a major role in the retinal light adaptation and may account for the duration of the negative afterimage. Here we present results showing a significant reduction of negative afterimage duration in PD patients. This supports the hypothesis that the retinal dopaminergic system may be the main cause for the long duration of negative afterimage. We suggest that the observed reduction of afterimage duration is due to possible dopaminergic deficiency in patients with Parkinson's disease.

Brain metastases in patients with diagnosed versus undiagnosed primary tumor

OBJECTIVES

To propose a diagnostic work-up specifically tailored to the undiagnosed primary (UDP) tumor patients.

METHODS

To investigate the distribution of primary tumors and presenting symptoms in UDP versus diagnosed primary (DP) patients, 50 consecutive patients with diagnosis of brain metastasis in Shohada Hospital, Tehran, Iran from January 2001 to December 2005 were included in this study. Univariate analyses were performed to assess the difference of various variables between DP and UDP patients.

RESULTS

The UDP patients represented 46% of all. Aphasia was significantly more common in the UDP group (p=0.0008) and ataxia in the DP group (p=0.04). The source of the metastases proved to be different between the 2 groups of interest (p=0.0006). The lung was the most frequent primary site in both groups. Among all UDP patients, a primary tumor in a location other than the lung was only found in 17% of patients. This study validated the hypothesis that the distribution of primary tumors differs between DP and UDP patients.

CONCLUSION

If lung investigation fails to disclose the location of primary tumor, the patient is unlikely to benefit from extensive paraclinical investigation. In such a situation, a neurosurgical procedure should be considered the most appropriate second step to be taken.

Management of cystic craniopharyngiomas with intracavitary irradiation with 32P

BACKGROUND

Cystic craniopharyngiomas are the most frequent intracranial neoplasm of nonglial origin in children. Follow-up data were analyzed to assess the value of intracavitary irradiation with stereotactically applied 32P radioisotopes for the treatment of patients with craniopharyngioma cysts admitted to Shohada Tajrish Hospital, Tehran, Iran, between 1998 and 2005.

METHODS

Patients with predominantly cystic craniopharyngiomas, who underwent stereotactic intracavitary irradiation, were followed for tumor response and complications. Beta-emitting 32P isotopes were injected into cysts using a computed tomography-guided and computer-assisted three-dimensional stereotactic treatment planning and application system. The cumulative dose to the inner surface of the cyst wall was 250 Gy.

RESULTS

Twenty-two (12 females and 10 males) patients with a mean+/-SD age of 14.0+/-6.6 (range: six to 35) years were studied. The tumor response rate gained with 32P-labeled chromic phosphate was 73% (16 of 22 cysts). The mean+/-SD survival after intracavitary irradiation was 25.4+/-6.8 (95% CI: 12.0 - 38.7) months.

CONCLUSION

Intracavitary irradiation using 32P is highly effective in the treatment of cystic craniopharyngiomas. In patients with solitary cyst treated exclusively with this method, it has been the only necessary therapy over a long period. It seems reasonable to recommend intracavitary irradiation as the initial treatment for selected patients and as palliative therapy in those with recurrence.

Bilateral traumatic hypoglossal nerve transection in a blast injury

BACKGROUND

The hypoglossal nerve supplies motor function to the tongue.

CASE DESCRIPTION

A 21-year-old man was injured in a blast injury to his mandible, resulting in severe maxillofacial hemorrhaging. Irreversible injury was evident from lack of improvement to tongue; patient underwent transplantation by end-to-end coaptation of right injured nerve 6 months after injury, with subsequent repair to left nerve 2 months later. At 11-year follow up, there was acceptable force and normal motor activity. Only speech, mastication, and swallowing did not return to normal despite prolonged physiotherapy.

CONCLUSION

In hypoglossal nerve injury, the proximity of the injury site to the primary muscle and, therefore, the short time required for the nerve fibers to repair toward the muscle are expected to predict an excellent outcome after transplantation. However, this is not usually the case, as in our patient.

Cerebral lymphoma: clinical and radiological findings in 90 cases

BACKGROUND

Cerebral lymphoma is a rare non-Hodgkin's lymphoma, which involves the brain primarily or after systemic involvement. Because of its infiltrating nature and its sensitivity to radio- and chemotherapy, surgical removal has a limited role in its treatment and only a stereotactic biopsy is necessary for confirming the diagnosis.

METHODS

The data from all cases in whom the cerebral lymphomas were pathologically confirmed and were admitted to the Neurosurgery Department of Shohada Hospital for stereotactic biopsy during a 15-year period were analyzed retrospectively.

RESULTS

The male to female ratio was 1.3:1 and the mean age was 51.7 years. Sixty-seven percent of the patients had multiple lesions and the remainder had solitary lesions. The most common site of involvement in patients with multiple lesions was diencephalon and in patients with solitary lesions was frontal lobe. The mean duration from symptom presentation to stereotactic biopsy was three months. Systemic lymphoma was detected in nine patients and three patients had a history of immunosuppressive drug consumption. The most common presenting symptom was headache in 42% and the most common sign was paresis in 59% of the patients. In 53 patients, follow-up was performed by phone call. Of these, seven cases had died without treatment in an average of 40 days after diagnosis, 28 patients died despite adjuvant treatment in an average of 8.5 months, and 18 cases were alive by the time of last follow-up with average of 17 months. Overall survival of the treated group was 12 months.

CONCLUSION

There was no mortality related to stereotactic biopsies in these patients.

Dosimetry of 32P radiocolloid for treatment of cystic craniopharyngioma

In Tajrish Shohada Hospital, patients with either cystic craniopharyngiomas or cystic astrocytomas have been treated with (32)P radiocolloid by stereotactic procedure. The total activity was prescribed for delivery dose between 200 and 300 Gy to the cyst wall thicknesses of 1-3mm. In this project, MD-55-2 radiochromic film was utilized to determine the dose distribution around the source. The film dosimetry data were compared with Monte Carlo simulated values calculated with MCNP4C code. In addition, the clinical and dosimetric factors such as the cyst volume, and method of radiocolloid injection were evaluated. The required activity and distribution of radial dose in and out of cyst wall have been investigated.

Effect of Vim thalamic DBS in Parkinson’s disease on F wave duration

F waves were recorded from abductor hallucis muscle in eight Parkinsonian patients with deep brain stimulation (DBS) electrodes surgically implanted in their Vim thalamic nucleus in two conditions of DBS ON and OFF. Patients with relatively anteriorly located electrodes exhibited a significant reduction in F wave duration and also in the UPDRS rigidity score of the corresponding foot when the DBS was ON. In contrast, patients with relatively posteriorly located electrodes exhibited no significant difference in F wave duration in the two DBS ON and OFF conditions. The rigidity UPDRS score in the corresponding foot diminished very little in the latter group. Both groups had great improvement in their tremor at rest UPDRS score in that foot when the DBS was ON. Vim surgery is generally accepted to affect tremor mechanisms. However, surgical intervention in anterior parts of Vim has been reported to affect rigidity mechanisms. This correspondence of these two symptoms of rigidity and tremor with the two locations of anterior and relatively posterior Vim may indicate the contribution of mechanisms of rigidity, but not tremor, in enhancement of F wave duration and hyper excitability of spinal motoneuron.

Resistance of peripheral and sub-cortical somatosensory pathway to electrical noise

The somatosensory system is vulnerable to large amounts of noise distortion. But how does the central nervous system distinguish the peripheral inputs which carry information to the brain from that which does not possess information? To address this question we studied the effect of electrical stimulation of the median nerve on tactile spatial frequency perception in healthy subjects and Parkinson's disease (PD) patients. Subjects were categorized in two groups (healthy and PD patients) and were asked to report if a test tactile frequency pattern (TFP) was the same as the reference TFP given to the other hand. In each case stimulation was either present or absent on the median nerve of the hand holding the test pattern. We observed no impairment of tactile performance in the presence of electrical stimulation of the median nerve. This result together with previous work on direct stimulation of the somatosensory relay nucleus of the thalamus in which the same result of no impairment of the tactile discrimination task was observed suggest a high degree of noise tolerance exists in the somatosensory pathway.

Tactile discrimination task not disturbed by thalamic stimulation

The major pathway of human somatosensation passes through the ventrocaudal nucleus (Vc) of the thalamus. We tested the effect of direct electrical stimulation of the Vc on tactile discrimination in 5 Parkinson patients undergoing stereotactic thalamotomy. Raised gratings with lines 3, 4, or 6 mm apart were used. Patients had to actively touch test patterns placed in the hand contralateral to the thalamus under operation and compare it with a reference 3-mm grating held continuously in their other hand. Their performance was best for 6-mm, followed by 3-mm and then by 4-mm patterns regardless of electrical stimulation. Under Vc stimulation, patients recognized the 4-mm gratings slightly better. This can be explained either by the nature of thalamocortical interaction, which makes it resistant to external noise, or by the involvement of other pathways that circumvent the effect of thalamic stimulation.

Stereotactic management of bacterial brain abscesses

BACKGROUND

CT and MR guided stereotactic techniques have provided promising results in the management of brain abscesses. We reviewed our results of stereotactic management of brain abscesses in 20 consecutive patients with 28 abscesses from 1986 to 1993.

METHODS

13 abscesses were in the cerebral hemispheres, 12 in the cerebellum, 2 in the pons and 1 in the thalamus. The bacterial organism was isolated in 12 of the 20 cases. All patients, except one who had a tuberculous abscess, were on antibiotics for less than 7 weeks.

RESULTS

Although there were 3 patients in coma before surgery, the mortality rate was zero and 17 patients had an excellent recovery with 3 patients having a persistent mild neurologic disability. Stereotactic aspiration of the largest lesion in the patients with multiple brain abscesses combined with intravenous antibiotic therapy was sufficient for the resolution of all lesions. Two of our patients treated with antibiotics alone showed abscess progression with neurologic worsening.

CONCLUSION

Stereotactic aspiration is safe, accurate, and when combined with the appropriate antibiotics, should be considered the procedure of choice in the management of brain abscesses.

Thalamotomy for essential and cerebellar tremor

Thalamotomy significantly suppressed essential tremor in 86% of patients and restored the ability to hold a glass to drink in 81% in the long term, but tremor recurred in 5/21 patients up to 5 years postoperatively, unlike parkinsonian patients whose tremor seldom recurs after 3 months. In multiple sclerosis (MS), 67% of those followed showed sustained significant suppression of tremor, 67% sustained improvement in dexterity, 50% in drinking; tremor recurred up to 5 years postoperatively. In other cerebellar tremors, 52% of those followed enjoyed lasting significant relief of tremor, 55% in dexterity, 45% in drinking, tremor relief being best in poststroke cases. Chronic thalamic stimulation may be the preferred therapy in MS and other cerebellar tremors.