Types of the cerebral arterial circle (circle of Willis) in a Sri Lankan population.

BACKGROUND: The variations of the circle of Willis (CW) are clinically important as patients with effective collateral circulations have a lower risk of transient ischemic attack and stroke than those with ineffective collaterals. The aim of the present cadaveric study was to investigate the anatomical variations of the CW and to compare the frequency of prevalence of the different variations with previous autopsy studies as variations in the anatomy of the CW as a whole have not been studied in the Indian subcontinent. METHODS: The external diameter of all the arteries forming the CW in 225 normal Sri Lankan adult cadaver brains was measured using a calibrated grid to determine the prevalence in the variation in CW. Chisquared tests and a correspondence analysis were performed to compare the relative frequencies of prevalence of anatomical variations in the CW across 6 studies of diverse ethnic populations. RESULTS: We report 15 types of variations of CW out of 22 types previously described and one additional type: hypoplastic precommunicating part of the anterior cerebral arteries (A1) and contralateral posterior communicating arteries (PcoA) 5(2%). Statistically significant differences (p < 0.0001) were found between most of the studies except for the Moroccan study. An especially notable difference was observed in the following 4 configurations: 1) hypoplastic precommunicating part of the posterior cerebral arteries (P1), and contralateral A1, 2) hypoplastic PcoA and contralateral P1, 3) hypoplastic PcoA, anterior communicating artery (AcoA) and contralateral P1, 4) bilateral hypoplastic P1s and AcoA in a Caucasian dominant study by Fisher versus the rest of the studies. CONCLUSION: The present study reveals that there are significant variations in the CW among intra and inter ethnic groups (Caucasian, African and Asian: Iran and Sri Lanka dominant populations), and warrants further studies keeping the methods of measurements, data assessment, and the definitions of hypoplasia the same.

Comparison of the configuration of the posterior bifurcation of the posterior communicating artery between fetal and adult brains: A study of a Sri Lankan population.

OBJECTIVE: The purpose of this study was to examine the degree of contribution from the vertebrobasilar and carotid systems to the origin of the PCA in fetal autopsy brains of last trimester of pregnancy and to compare with published data on the configuration of adult and fetal brains in a population of Sri Lankan origin. MATERIALS AND METHODS: The external diameter of the PcomA, pre-communicating part (P1), and the post-communicating part (P2) of posterior cerebral artery (PCA) of 34 fetal brain in the last trimester of pregnancy (30 to 40 weeks of gestation) was measured using a stereomicroscope equipped with a micrometer calibrator. RESULTS: The blood supply to the occipital lobe mainly via the PCA was seen in 25 (59%) of fetal brains as compared to that in the literature 220 (93%) in adults brains and the blood supply to the occipital lobe mainly via the internal carotid artery (ICA) was seen in 16 (34%) of fetal brains as compared to 25 (7%) of adults brains (P < 0.0001), transitional configuration where the PcomA is equal in diameter to P1 segment of the PCA was seen in 5 (7.4%) of fetal brains and 8 (2%) of adults brains. CONCLUSIONS: The present study reveals that from the newborn to the adult there is shift from carotid system to the vertebrobasilar system, this justifies further studies on different racial and geographic regions which may give a clearer picture about the cerebral hemodynamics from childhood to adult.

Variation in the origin of the posterior cerebral artery in adult Sri Lankans.

BACKGROUND: The degree of contribution from the vertebro-basilar and carotid systems to the origin of the posterior cerebral artery (PCA) is of clinico-anatomical importance. Three configurations in the bifurcation of the posterior communicating artery (PcomA) have been described, foetal, transitional and adult. OBJECTIVE: To examine the extent of contribution from the vertebro-basilar and carotid systems to the origin of the PCA in adult autopsy brains in subjects who had died of causes unrelated to the brain. MATERIALS AND METHODS: The external diameter of the PcomA, pre communicating part (P1) and the post communicating part (P2) of PCA in 225 normal Sri Lankan adult cadaver brains was measured using a calibrated grid. RESULTS: The adult configuration was present in 220 (93.3%); (bilaterally in 200 (88.8%), and unilaterally in 20 (8.8%) ten on each side. Foetal configuration was seen in 17 (4.4%); bilaterally in 3 (1.3%), and unilaterally in 14 (6%) 8 on the left and 6 on the right. Transitional configuration was seen in 8 (2.2%); bilaterally in 2 (0.9%), and unilaterally in 6 (2.5%) 2 on the left and 4 on the right. CONCLUSION: This study reveals that the internal carotid artery (ICA) provided the major supply to the PCA in 4.4% of foetal and 2.2% of transitional configurations. The adult configuration was present in 220 (93.3%), the highest recorded in the literature. This finding may be of relevance to vertebrobasilar ischaemia and infarcts in the territory of the PCA.

Prevalence of typical circle of Willis and the variation in the anterior communicating artery: A study of a Sri Lankan population.

OBJECTIVE: To determine the extent of hypoplasia of the component vessels of the circle of Willis (CW) and the anatomical variations in the anterior communicating artery (AcomA) in the subjects who have died of causes unrelated to the brain and compare with previous autopsy studies. MATERIALS AND METHODS: The external diameter of all the arteries forming the CW in 225 normal Sri Lankan adult cadaver brains was measured using a calibrated grid to determine the occurrence of "typical" CWs, where all of the component vessels had a diameter of more than 1 mm. Variations in the AcomA were classified into 12 types based on Ozaki et al., 1977. RESULTS: 193 (86%) showed "hypoplasia", of which 127 (56.4%) were with multiple anomalies. Posterior communicating artery (PcoA) was hypoplastic bilaterally in 93 (51%) and unilaterally in 49 (13%). Precommunicating segment of the posterior cerebral arteries (P1) was hypoplastic bilaterally in 3 (2%), unilaterally in 14 (4%), and AcomA was hypoplastic in 91 (25%). The precommunicating segment of the anterior cerebral arteries (A1) was hypoplastic unilaterally in 17 (5%). Types of variations in the AcomA were: single 145 (65%), fusion 52 (23%), double 22 (10%) [V shape, Y shape, H shape, N shape], triplication 1 (0.44%), presence of median anterior cerebral artery 5 (2%), and aneurysm 1 (0.44%). CONCLUSION: The occurrence of "typical" CW in autopsy brains was rare. Further studies would be necessary to determine if these anatomical variations could predispose to cerebral ischemia and premature stroke in the Sri Lankan population.

Brain abscess caused by Nocardia asteroides.

A case of Nocardia brain abscess in a patient receiving immunosuppressives is reported. The diagnosis was made by aspiration and culture of pus from the abscess. This is the first documented case of Nocardia brain abscess in Sri Lanka.

Clinical correlation of urodynamic findings in patients with localized partial lesions of the spinal cord and cauda equina.

Urodynamic studies were undertaken in 70 patients with incomplete, confirmed, localized lesions involving the spinal cord and cauda equina, irrespective of clinically evident bladder disturbances. Both detrusor and urethral function were simultaneously evaluated and correlated with neurological deficits and symptoms of lower urinary tract dysfunction. It was evident that in those patients with localized spinal cord lesions, lower urinary tract disturbances were closely associated with disturbances of pinprick sensation. Clinically silent bladder and sphincter dysfunction was encountered in 14% of the patients, and the number of asymptomatic patients was significantly higher among those with upper motor neuron lesions. Incontinence was associated predominantly with conus lesions; however, the other symptoms had no relationship to the site of the lesion. Symptoms such as urgency, incontinence, and nocturnal incontinence were associated with detrusor hyperactivity, and urinary retention was associated with urethral overactivity and dyssynergia. The urodynamic findings could explain the pathogenesis of the symptoms in most instances, but were not necessarily related to them. It is concluded that the pathways subserving lower-urinary-tract function are closely associated with the pathways subserving pinprick sensation, and that a lesion along the spinal axis can affect the bladder, sphincter, or both in a variety of ways, thus leading to the widely variable clinical findings associated with neurogenic lower urinary tract dysfunction.

Urethral function in neurological disorders of the lower urinary tract.

Simultaneous measurements of intravesical pressure, urethral pressure, and electromyographic activity of perianal muscles were performed during bladder filling and voiding in 56 patients with neurogenic lower urinary tract dysfunction. In 21 patients simultaneous measurements were taken of the EMG activity of the striated-muscle external urethral sphincter. During bladder filling the urethral pressure was found to correspond to the EMG activity of both muscles only in those patients with normal urethral pressure. During voiding the EMG activity of neither muscle corresponded well with changes in urethral pressure. The EMG activity of perianal muscles corresponded to the activity of the external urethral sphincter during filling of the bladder but not during voiding.

Significance of detrusor compliance in patients with localized partial lesions of the spinal cord and cauda equina.

Detrusor compliance was measured by cystometry irrespective of any symptoms of lower urinary trace dysfunction in 70 patients with localized, partial, surgically treatable lesions of the spinal cord and cauda equina. Compliance was found to be normal in all patients with upper motor neuron lesions; reduced compliance was encountered only in those with lower motor neuron lesions. Reduced compliance was closely associated with lesions of the conus medullaris and with detrusor hyperreflexia, and it is therefore likely that the mechanism of compliance involves a significant neural component. Incontinence, particularly nocturnal incontinence, was encountered more frequently among those with reduced compliance than in those with normal compliance, whereas retention of urine was comparatively rare with reduced compliance.

Detrusor hyperreflexia in neurogenic bladder disorders caused by localized partial lesions of the spinal cord and cauda equina.

In 70 patients studied by cystometry, detrusor hyperreflexia seen with localized partial lesions of the spinal cord and cauda equina could be differentiated into two types. In one type, in which the hyperreflexia was of a reflex nature and bladder compliance was unchanged, the detrusor contractility was described as compliant hyperreflexic. In the other type, in which the contractions were of a rhythmic nature and accompanied by reduced compliance, the contractility of the detrusor was described as noncompliant hyperreflexic. The compliant hyperreflexic contractions correlated well with signs of upper motor neuron disturbance, the noncompliant hyperreflexic contractions with lower motor neuron disturbance.