Structural Changes in the Insular Cortex in Alcohol Dependence: A Cross Sectional Study

Article excerpt

Objective: This study was conducted to determine the changes in the insular cortex in alcohol dependent subjects, and to compare the same with controls, the associated clinical findings.

Methods: The study group consisted of 30 subjects with alcohol dependence syndrome (ADS) selected randomly from the out patient services of the department of psychiatry of a tertiary care hospital. The control group consisted of 30 matched subjects selected randomly from the out patient department and from patients screened for uncomplicated headache. Both groups were examined by a computerized scan (CT), and Mini Mental Status Examination (MMSE).

Results: Chi square, and t' test were done after calculating the Evan's ratio. The two groups were compared to assess the cortical atrophy and ventricular enlargement. Cognitive functions were tested by MMSE, and the scores were compared. Atrophy was significantly higher in the experimental group; however, it was not significant. Cognitive functioning was found to be significantly impaired in the experimental group.

Discussion: The study showed that alcohol dependence leads to cortical atrophy which is age independent. The statistically significant disturbance in the MMSE scores along with the frontal and parietal cortical atrophy is also indicative of the insular cortex involvement in the experimental group .

Conclusion: Alcohol dependence leads to cerebral atrophy along with the involvement of the insular cortex.

Keywords: Alcohol related disorders, Cerebral cortex, Cognition, Computed tomography

The insular cortex is a cerebral cortical structure which lies deep within the lateral fissure in between the temporal lobe and the frontal lobe (1). The overlying cortical areas are the operculum which is formed from the parts of the enclosing frontal, temporal and parietal lobes. The insula plays a role in diverse functions usually linked to emotion or regulation of the body's homeostasis (2). These functions include perception, motor control, self-awareness, cognitive functioning, and inter personal experiences. Hence, it is implicated in the development of psycho pathology (3). Alcohol consumption is widespread in India. Prevalence of alcohol abuse in India is 6.9 per thousand with urban and rural rates being 5.8 and 7.3 per thousand respectively (4, 5).

CT scan is a widely available imaging technique that can detect gross neuropath logical changes like cortical atrophy, ventricular enlargement, tumor, calcification, cerebro vascular disease. It is a reliable, economical, and effective imaging technique which can detect

unsuspected neuropath logical conditions (6). CT scan is a relatively simple technique which relies on the

Same physics as conventional x-ray; structures are distinguished from one another by their ability to absorb energy from x-rays. It ,however, has some important disadvantages like exposure to ionizing radiation, limited visualization of structures in the transverse plane, relatively poor contrast between white and gray matter, poor visualization of posterior cranial fosse structures. Despite all this, CT scan is a useful technique for measuring intracranial structural changes (6).A number of functional brain imaging studies have shown that the insular cortex is activated when drug abusers are exposed to environmental cues that trigger cravings (2, 7). This finding has been shown for a variety of drug abuse, including cocaine, alcohol, opiates and nicotine (7). Despite these findings, the insula has largely been overlooked with regards to its role in drug addiction, perhaps because it is not known to be a direct target of the mesotelencephalic dopamine system which is central to current dopamine reward theories of addiction(8). To date, several researches have been done on the structural brain changes in alcohol dependence. Some have found frontal lobe change (9-12), others have found parietal (13) or temporal lobe atrophy (14) or ventricular dilatation (15) but none has focused attention on the insular cortex. …