Alicia Merlo

Inversion of the hemispheric laterality of the anterior cingulate gyrus in schizophrenics

The anterior cingulate gyrus (acg) is involved in mechanisms of attention and emotion, where the right hemisphere is considered to be dominant. One of the models for neuropsychological dysfunction in schizophrenia suggests an impairment in the balance of lateralized functions. Fourteen adult human female brains, having no macroscopic lesions, were used in this study. Seven brains came from female patients with clinical diagnoses of residual schizophrenia (DSM-III-R; APA 1987). Seven female brains were used as controls. Thirteen male brains were also studied, with the sole purpose of establishing the typicality of the female controls. All schizophrenic brains were age matched with control brains. Right laterality for weight (71.4%) and surface (85.7%) was observed in the acg of female control brains. The inversion of this laterality in a significant number of the schizophrenic cases was the most relevant finding in this study.

COMPENSACIÓN: UN NUEVO CONCEPTO RELACIONADO CON LA LATERALIDAD CEREBRAL. SU APLICACIÓN A REGIONES DEL LÓBULO FRONTAL, INCLUIDA EL ÁREA MOTORA DEL LENGUAJE (DE BROCA)

: Cuando se determina la asimetria de una estructura bilateral formada por subregiones asimetricas con lateralidades opuestas, queda enmascarada (compensada), total o parcialmente, la existencia de las diferencias interhemisfericas de tales subregiones. Para cuantificar esta realidad, hemos establecido un nuevo parametro: la compensacion. El objetivo del presente trabajo, realizado en cerebros humanos postmortem, esta dirigido a determinar los porcentajes de compensacion, de asimetria de peso y de superficie cortical, de tres regiones cerebrales pertenecientes al lobulo frontal: 1. El area de motora del lenguaje (de Broca). 2. La porcion anterior del giro frontal inferior. 3. El giro frontal inferior en su totalidad. Para valores de peso y de superficie cortical para el area motora del lenguaje los porcentajes de casos con compensacion parcial o total son, respectivamente, 50 y 42%; para la porcion anterior del giro frontal inferior 70 y 67%; y para el giro frontal inferior en su totalidad 96 y 96%. En este ultimo el porcentaje de casos con compensacion es significativamente mayor que en las otras dos regiones (Chi2). Similares valores porcentuales de asimetria pueden darse en casos con muy diferentes valores porcentuales de compensacion. Esto demuestra que con el solo calculo de la asimetria se enmascaran aspectos de las diferencias interhemisfericas. De ahi que ambos valores son complementarios

VARIACIONES ANATOMICAS DEL CANAL CONDILEO

The variations in vascular anatomy and cranial foramina have important implications for their accurately recognition as normal or pathological. The condylar vein exits the skull base through the condylar canal, communicating the jugular foramen and the condylar fossa. The main purpose of this report was to asses the prevalence and normal anatomical patterns of the condylar canal . Eighty-one cadaveric skull base specimens were retrospectively examined for the unilateral or bilateral presence or absence of the canal. In addition, the condylar canal was classified for its relationship with the sigmoid-lateral sinus, in two types: Intrasinus canal type and Retrosinus canal type. The condylar canal was found bilaterally in 25 skulls (30.8% ); unilaterally in 25 skulls (30.8%) and was absent in 31 specimens (38.2%). A higher prevalence of Intrasinus canal type was found (54.3% ). Although it was only identified 2 cases (2.4% ) of retrosinus canaltype, associated forms (4.9%) were discovered during examination. Of the unilateral cases, 14 cases were right sided and 11 cases were left sided (17.8% and 13.5% among all cases, respectively). The condylar canal has two anatomical patterns: intrasinus canal type and retrosinus canal type. This structure may have some clinical relevance, and it should not be misinterpreted as abnormal during image studies

LAS RELACIONES DE DOMINANCIA EN EL LÓBULO LÍMBICO

La dominancia morfologica de regiones cerebrales suele expresarse en funcion del numero o porcentaje significativo de casos que presenta una misma lateralidad hemisferica. Estimamos que la evaluacion de la dominancia debiera complementarse mediante una expresion relacionada con la magnitud relativa de los valores de las asimetrias de los casos con lateralidades opuestas, con significacion estadistica, util para comparar la dominancia de diferentes regiones cerebrales. Para tal fin, hemos desarrollado una nueva expresion, que presentamos en el 250 Congreso Argentino de Neurociencias (2000), a la que denominamos relacion de dominancia (rD). El objetivo del presente estudio fue determinar las rD con su significacion estadistica, de pesos y superficies corticales expuestas y profundas del lobulo limbico (LL) y de sus giros -giro del cingulo anterior (CA), giro del cingulo posterior (CP) y giro parahipocampal (PH)- en 20 cerebros humanos adultos, postmortem, procesados segun nuestro metodo (Arch. Neurol. 46: 307-310, 1989; Rev. Chil. Anat. 17:175-81, 1999). La rD esta basada en la correlacion no parametrica de Spearman. Las variables que se enfrentan en la correlacion corresponden a la lateralidad con su signo (negativo si es izquierda y positivo si es derecha) y al valor absoluto de lateralidad. Su rango esta comprendido entre - 1 y +1. Su signo resulta negativo si la dominancia es izquierda y positivo si es derecha. Son estadisticamentre significativas (p<0.001) las rD de peso y de superficie cortical del CA ( 0.97 y 0.99) y del LL (0.88 y 0.94). La diferencia entre ellas es significativa (p<0.05). Las rD, cuantificando las lateralidades relativas del CA y del LL, complementan las expresiones de dominancia derecha de ambas estructuras, basadas en el porcentaje significativo de casos que comparten dicha lateralidad hemisferica y muestran ausencia de significacion estadistica de dominancia en el resto de giros del lobulo

Los giros del lóbulo frontal: estudio postmortem

The objective of the present work was to study the lobus frontalis in postmortem human brains in order to obtain weight as well as superficial and deep cortex values of the lobus and its gyri and quantitative ratios among these values. Twelve brains obtained from right-handed subjects aged between 30 and 55 years having no visible macroscopic neurologic lesions were fixed in formaldehyde (5%) and processed using a method developed in our laboratory (Arch. Neurol., 46:307; 1989). Absolute and percent values, as well as weight/cortical surface ratios and correlations of the gyri of the lobus frontalis - regio orbitalis, cinguli, superior+medium, inferior and precentralis - were obtained. The cortical surface of the right gyrus cinguli is significantly larger than the contralateral one. The statistically lower weight/cortical surface ratio corresponds to the regio orbitalis and the higher one to the gyrus precentralis. The regio orbitalis supplies a higher percentage in cortical surface than in weight to its respective lobus frontalis; the opposite occurs with the gyrus precentralis. The right gyrus cinguli supplies a higher percentage in weight than in cortical surface than the left one. The Pearson coefficient of correlation between the values (absolute and percent) corresponding to weight and cortical surface between homologous gyri of both hemispheres are positive.The correlations between weight absolute as well as percent values and those of the respective cortical surface are positive, excellent and highly significant. The higher percentage of cases with right laterality corresponds to the gyrus cinguli and that with left laterality to the gyrus frontalis inferior. Modifications that could occur in brains from psychiatric and neurologic patients could alter some of these values and relationships, as for example in schizophrenia in which we found an inversion of the gyrus cinguli anterior laterality (ALBANSE et al., 1995)