Visual Evoked Potential in Megaloblastic Anemia : A Cross Sectional Study

Megaloblastic anemia is the second mostcommon type of anemia after iron deficiencyanemia. Itresults from faulty DNA synthesis attributed to vitamin B12 or folic acid deficiency & may be associated with neuropathy which can lead to substantial morbidity if unrecognized or misdiagnosed.The aim of the study was to evaluate the Visual evoked potential (VEP) in megaloblastic anemia. VEP provide a non-invasive method of assessingneurological function. A delayed VEP supports the diagnosis of optic neuropathy.The study was conducted in 100 subjects50 controls and 50 patients of megaloblastic anemia diagnosed by low haemoglobin levels along with increased MCV, low serum vitamin B12 or bone marrow changes or both. Patients were tested for visual acuity, field of vision and colour vision. Pattern reversal VEP was carried out. P100 latency and amplitude were measured.VEP revealed prolongation of P100 latency when compared with control group which was statistically significant. VEP can be used as an early indicator of optic nerve involvement in patients with asymptomatic megaloblastic anemia. Indian J Physiol Pharmacol 2017; 61(3) : 290–294 *Corresponding author : Dr. Soniya Dattatray Phartale, Department of Physiology, Govt Grant Medica l Col lege & JJ Hospi ta l , Bycu l la , Mumbai – 400 008; Email: soniyavarge@gmail.com (Received on March 12, 2017) the Indian population, as most of the Indian population is vegetarian, especially Hindus and Jains who exclude animal protein from their diet for religious or social reasons. Deficiency of vitamin B12 results in asynchrony in the maturation of the nucleus and cytoplasm of rapidly regenerating cells. In the haematopoietic system this asynchrony results in abnormal nuclear maturation with normal cytoplasmic maturation, ineffective erythropoiesis, intramedullary haemolysisand typical morphological abnormalities in the blood and marrow cells leading to the formation of megaloblasts with the development of a macrocytic anaemia (1). Introduction Megaloblasticanemiaresults from impaired DNA synthesis due to vitamin B12 or folic acid deficiency. The only natural sources of vitamin B12 are of animal origin i.e. meat, dairy products and fish. Therefore the prevalence of megaloblastic anemia is higher in Indian J Physiol Pharmacol 2017; 61(3) Visual Evoked Potential in Megaloblastic Anaemia 291 acuity, field of vision& colour vision to rule out any asymptomatic ophthalmic & neurologicdiseases affecting eyes. Then Pattern reversal VEP was carried out. Patients were explained about the test to ensure full co-operation and were instructed to avoid oil/hair spray after the last hair wash before test was performed. VEPs were performed with the patient’s appropriate refractive correction. The patient was seated comfortably on a chair at 100 cm distance from the visual stimulus. To record the VEP, standard silver-silver chloride disc EEG electrodes were fixed to the scalp with conducting paste. The recording (active), reference & ground electrodes were attached on occiput at Oz, forehead at Fpz& the vertex at Cz as per 10-20 international system respectively. The impedance of the scalp-electrode connection was kept below 5 kΩ. Stimulation was provided with black & white checkerboard of size 14×16" at the rate of 1 Hz. Number of epoch analysed were 100 using band pass filter 1-300 Hz. The patients were asked to fix the gaze at the center of the screen. The waveform of the pattern-reversal VEP normally consists of three principal features: an init ial negativity with a latency of approximately 70 to 80 msec (N75), a larger positive component with a latency of approximately 90 to 110 msec (P100), and a large negative component with a latency of approximately 130 to 140 msec (N135). Then P100 latency and amplitude were measured. Statistical analysis The data is expressed as Mean±SD for each group. Unpaired t test was performed to compare P100 latency and amplitude between the two study groups. The level of significance was at p<0.05.