Prueba del trazo en bipolares con hiperamonemia secundaria a ácido valproico / Trial making test in bipolar patients with hyperammonemia secondary to valproic acid

ABSTRACT

The TMT (Trail Making Test) evaluates psychomotor velocity (in part A of the test) and it gives an appreciation of the capacity of the person to change strategies, as well as the executive function and working memory (in part B of the task). The negative cognitive impact of high ammonia levels in bipolar patients has not been studied yet. Twelve bipolar patients who where under valproic acid (AV) treatment, not previously exposed to this mood stabilizer, showed an increase of the ammonia levels (with a mean of 79 ug/dl) after four weeks receiving the drug; these patients responded the Mini Mental State Examination (MMSE) and the TMT (Parts A and B). Four weeks after AV was retired and the treatment had been changed to another mood stabilizer, ammonia levels became normal and their mood became euthimic (as the HAMD-17 and YMRS). Sequenced ANOVA tests were performed to the obtained data in both controls weeks 4 and 8) and the results were as follows MMSE showed no statistical differences between both controls. Statistical differences were seen with high ammonia levels in part A of the TMT between both groups. This suggests a better performance in this test with normal ammonia levels. Statistical differences were also observed in part B of TMT, even with a significance level „´ .001. Besides, clinical regressions of TMT B scores are observed, meaning that the variability between patients diminishes, which indicated that the performance of this instruments became more homogeneous. This suggests that bipolar patients with moderate elevation of ammonia levels only present alterations at more specific and detailed neurocognitive tasks.

RESUMEN

La prueba del Trazo (TMT) evalúa velocidad psicomotora (parte A) y que aprecia la capacidad para cambiar estrategias, evaluar función ejecutiva y memoria de trabajo visoespacial en parte B. El impacto cognitivo de la hiperamonemia no ha sido estudiado en bipolares. A 12 bipolares en tratamiento, no expuestos antes a ácido valproico (AV) quienes, a cuatro semanas de su incorporación, presentan hiperamonemia (promedio 79 ug/dl), se les aplica Mini Mental State Examination (MMSE) y TMT (Partes A y B). Se cambia AV y cuatro semanas después se repiten pruebas, con amonemia normal y manteniéndose eutímicos según HAMD-17 y YMRS. Se lleva a cabo un ANOVA de medidas repetidas sobre los datos obtenidos en ambos controles (semana 4 y semana 8) y se obtienen los siguientes resultados. El MMSE no muestra diferencias estadísticamente significativas entre ambos controles. Con hiperamonemia se observan diferencias estadísticamente significativas en la parte A del TMT entre ambos controles. Ello sugiere un mejor desempeño en tal prueba con amonemia normal. Se observan también diferencias estadísticamente significativas en la parte B del TMT, incluso utilizando un nivel de significancia < .001. Además, clínicamente, en cuanto al desempeño en el TMT B se evidencia una regresión a la media, es decir, la variabilidad entre los sujetos disminuye, lo que indica que los desempeños se hacen más homogéneos. Lo anterior sugiere que bipolares con hiperamonemia moderada aguda sólo evidencian alteraciones frente a pruebas neurocognitivas más finas y específicas.