Delayed auditory conduction in diabetes: is metformin-induced vitamin B12 deficiency responsible?

The present study aims to evaluate the functional integrity of the auditory pathway in patients with diabetes taking metformin. A further aim is to assess its association with vitamin B12 deficiency induced by metformin. Thirty diabetics taking metformin and 30 age-matched non-diabetic controls were enrolled. Stimulus-related potentials and vitamin B12 levels were evaluated in all the subjects. The diabetics showed deficient vitamin B12 levels and delayed wave III latency and III-V interpeak latency in the right ear and delayed Na and Pa wave latencies in the left ear compared with the controls. The dose and duration of metformin showed no association with the stimulusrelated potentials. Therefore, although vitamin B12 levels were deficient and auditory conduction impairment was present in the diabetics on metformin, this impairment cannot be attributed to the vitamin B12 deficiency.

Effect of thyroxine therapy on autonomic status in hypothyroid patients.

The aim of the present study was to evaluate the impact of hypothyroidism on the autonomic regulation of the cardiovascular system by analyzing sympathetic and parasympathetic influences on the heart and the effect of thyroxine replacement. Thirty newly diagnosed female hypothyroid patients with mean age 32.73 +/- 9.98 years were recruited from the Thyroid Clinic, GTB Hospital, Delhi. Various Autonomic function tests to assess Basal heart rate variability, parasympathetic activity (E:I Ratio, 30:15 Ratio, Valsalva Ratio) and sympathetic activity (Postural Challenge test, Sustained handgrip test) were done before and after attainment of euthyroidism. There was significant increase in parasympathetic activity on achieving euthyroid state. The sympathetic activity too significantly improved after L-thyroxine supplementation. Lipid profile parameters significantly decreased after achieving euthyroid state. Our findings are consistent with previous reports that thyroxine therapy appears to restore the efferent vagal activity and alters the relative contribution of systems that maintain resting blood pressure and heart rate.

Cognitive status in hypothyroid female patients: event-related evoked potential study.

AIM: Higher brain functions are adversely affected in hypothyroid patients. The central nervous system features of hypothyroidism include mental retardation, various cognitive and memory deficits that have been evaluated by different neuropsychological tests. In the present study event-related potentials (ERPs) have been used to assess the cognitive status of hypothyroid patients before and after treatment. METHODS: Twenty-six newly diagnosed hypothyroid female patients with a mean age of 31.85 +/- 8.57 years and 26 female controls with a mean age of 30.92 +/- 7.24 years were the subjects of the study. The ERPs were recorded on a computerized evoked potential recorder using the 10-20 system of electrode placement and the standard auditory 'oddball' paradigm. The first recording of ERPs was done at the time of diagnosis and the second recording was done 3 months after the start of treatment in a euthyroid state. RESULTS: Prolongation of latencies was found in the early ERP components (N100, P200 and N200) in hypothyroid patients compared to controls, while no significant group differences were found on P300. In the hypothyroid group all the ERP latencies decreased significantly after attainment of euthyroidism compared to pretreatment values. ERP amplitudes revealed no significant group differences between hypothyroid patients and controls, but significant amplitude increases were found on the waves of N200 and P300 after treatment compared with pretreatment values in the hypothyroid group. CONCLUSIONS: Hypothyroid patients showed prolongation of latencies only in the early ERP components compared to controls. In hypothyroid patients, ERP findings indicate a speeding of sensory and cognitive processing in a state of euthyroidism compared to the pretreatment condition.

Auditory evoked responses in gestational diabetics.

Electrophysiological correlates of sensory function in diabetic pregnancy have not been documented. Present study reports changes in Auditory evoked responses (AER) in gestational diabetics when compared with normal pregnant controls. Human AER are generally classified into early Auditory brainstem responses (AER), Mid latency responses (MLR) and late Slow vertex responses (SVR). These potentials were recorded in 20 women with diabetic pregnancy using Ag/AgCl electrodes from Cz-A1 and Cz-A2 position on MEB 5200 Neuropack II ... plus (Nihon Kohden, Japan) Evoked Potential Recorder. The evoked potentials in gestational diabetics were compared with 20 age matched normal pregnant women using Student's t-test. Absolute latencies of waves I to V, Inter peak latencies I-III and I-V of ABR were significantly increased whereas amplitude of wave V decreased in diabetic pregnant women. No significant change in latency of any component of MLR was observed between the two groups whereas significant prolongation of latencies of all components of SVR was observed in diabetic pregnant women as compared to normal control group. These findings indicate prolongation of both peripheral transmission time (PTT) and central transmission time (CTT) in diabetic pregnant females. Prolongation of latencies of SVR components in this study implicates cortex in the central diabetic neuropathy in women with gestational diabetes.

Lipid peroxidation and antioxidant enzymes in gestational diabetics.

The exact pro-oxidant and antioxidant status in gestational diabetes is still unclear. To add new insight to the question, changes in the lipid peroxidation products (MDA) and activities of antioxidant enzymes: superoxide dismutase (SOD) and catalase in red blood cell hemolysates were evaluated in 20 women with gestational diabetes. 20 healthy pregnant women served as the control group. Statistical analysis was done using unpaired Student' t - test. Pregnant women with gestational diabetes showed an increase in lipoperoxidation products (P < 0.001) and a decrease in SOD activity (P < 0.01) as compared to normal pregnant women while no significant change was observed in catalase activity. These findings suggest increased oxidative stress and decreased detoxification or free radical scavenging capacity in pregnancy complicated by diabetes.

Status of pulmonary function tests in adolescent females of Delhi.

Progesterone is known to cause hyperventilation and hypercapnia in the luteal phase of a normal menstrual cycle. Viewing this fact lung functions were measured in 71 girls with a mean age of 14.5 years during their follicular and luteal phase of menstrual cycle. Subjects were grouped into I, II and III depending on the age range. Respiratory functions comprising of FVC, FIVC, TLC, RV/TLC, FEV1, FEV1/FVC, FRC, PEFR, FEF 25%, FEF 50%, FEF 75%, PIFR, RAW and KST respectively were performed using Spiro 232 of PK Morgan under standardized laboratory settings. The anthropometric parameters such as height, weight and arm span were also recorded. The majority of pulmonary functions reflect better values in luteal phase as compared with follicular phase however, a statistically significant higher results of FVC, FIVC, FEV1, and TLC were noticed in group I and group III. These observations suggest a possible role in increased level of progesterone in luteal phase on respiratory system.

Median nerve somatosensory evoked potentials correlation with physical parameters.

Somatosensory evoked potentials (SEPs) following median nerve stimulation of 25 medical students were recorded along with their height, age and upper limb length. Three major positive and negative peaks were recorded. P1 (16 msec), N1 (20 msec), P2 (28 msec), N2 (33 msec), P3 (43 msec), N3 (50 msec). Significant correlation (P value < 0.05) of N1 and P1 with height and limb length was observed. It is therefore suggested that studies involving SEPs must include physical parameters like age, height and limb length. Our future studies will indicate the accurate correction factor for these physical parameters.

Sensory nerve conduction during cold pressor response in humans.

A study was carried out to find the correlation, if any of autonomic responses and experimental pain induced during the cold pressor test (CPT) with the median nerve sensory conduction velocity (SCV). In 19 healthy subjects who volunteered for the study, the nondominant hand of each was subjected to the CPT and, pain parameters, heart rate, blood pressure and SCV were recorded. Dominant median nerve SCV was measured by orthodromic stimulation of the index finger and evoked responses were recorded at the wrist. In each subject, 32 evoked action potential responses were averaged to determine the SCV. Median nerve SCV of 57.8 +/- 5.2, 56.6 +/- 5.1, 57.0 +/- 5.2 and 57.8 +/- 5.1 m/sec were recorded before, during, immediately after and after ten minutes of the CPT, respectively. The SCV and the amplitude of the evoked response were significantly (P < 0.001 and P < 0.01 respectively) decreased during the CPT. A significant relationship (P < 0.05) was found between nerve conduction parameters and diastolic blood pressure recorded before the CPT. These findings suggest that sympathetic overactivity and/or cold induced pain interacts with sensory conduction in the contralateral median nerve so as to decrease its conduction velocity. There also exists a relationship between SCV and vasomotor mechanisms controlling peripheral resistance, and hence the diastolic pressure.

Brain stem auditory evoked responses during the cold pressor test.

This study was conducted to determine changes, if any, in Brain stem auditory evoked responses (BAEP's) during the cold pressor test (CPT) in healthy human subjects. Thirteen subjects (age 18-25 yrs) were selected for the study. Their BAEP's were recorded using standardized technique employing 10-20 international electrode placement system and sound click stimuli of specified intensity, duration and frequency. The standard CPT was performed in the non-dominant hand and the BAEP's, heart rate and blood pressure were recorded before and during the CPT. The values of absolute peak latencies and amplitude of evoked responses were statistically analysed. The amplitude of wave V showed a significant increase (P < 0.05) during the CPT (0.47 +/- 0.203 and 0.37 +/- 0.174 mu v before and during CPT respectively). This could be due to interaction of activated central ascending monoaminergic pathways or nociceptive afferents with the midbrain auditory generator so as to increase it's activity.