Morphology of acallosal brains as assessed by MRI in six patients leading a normal daily life

Abstract

The pattern of anatomical features of the brain revealed by magnetic resonance imaging (MRI) is described in six patients incidentally identified as having acallosal brains. The complex of morphological features associated with complete agenesis of the corpus callosum included lateral displacement of slitlike anterior horns of the lateral ventricles (bullhorn-like shape), dilatation of the posterior horns of the lateral ventricles, absence of the septum pellucidum, lateral displacement of the cingulate gyri, complete separation of fornices and the presence of the anterior commissure and longitudinal callosal bundles (Probst's bundles). No compensatory enlargement of the anterior commissure was seen in the patients. The planimetrically measured cross-sectional areas of the anterior commissures were between 2.0 and 4.2 mm2 (mean 3.1) (in ten normal subjects they were 4.5, SD 0.4; range 3.8-5.2 mm2) and were reduced in four and normal in two patients. Inconstant morphological features were an absence of the posterior commissure and a radial pattern of the sulci and gyri on the medial aspect of the hemispheres. Conventional clinical testing revealed no abnormalities except a slight impairment of walking heel-to-toe in two patients. None of the patients had subjective restrictions of activities of daily life, which shows the efficacy of unknown compensatory processes.

Malformations of the midline commissures: MRI findings in different forms of callosal dysgenesis

“…This was at least the case in the patients presented in this study; however, other authors have observed at least one patient without severe disability, also lacking CC and commissura fornicis [14]. This was at least the case in the patients presented in this study; however, other authors have observed at least one patient without severe disability, also lacking CC and commissura fornicis [14].…”

Transcallosal sensorimotor fiber tract structure‐function relationships

“…This is supported by the fact that iSPs are preserved in patients with subcortical cerebro-vascular lesions that interrupt the corticospinal tract but not the corpus callosum (Boroojerdi et al 1996). Furthermore, iSP is delayed or prolonged in neurological disorders affecting the CC such as multiple sclerosis (Schmierer et al 2000) and no detectable iSP is found in preschool children who have yet to develop a functionally competent corpus callosum (Heinen et al 1998), nor in patients with callosal agenesis (Meyer et al, 1995; 1998). Thus, the iSP has been proposed as a simple, clinical diagnostic tool for assessing callosal function (Meyer et al 1999).…”

Partial agenesis of the corpus callosum in spina bifida meningomyelocele and potential compensatory mechanisms

“…The child with the enlarged AC had complete CC agenesis. Meyer, Roricht, and Niehaus (1998) reported no enlargement of the AC in individuals with complete CC agenesis, the AC being smaller than normal in 4 and normal in 2. Because of these kinds of findings, Rauch and Jinkins (1994) had suggested that enlargement could serve as a compensatory mechanism in only a small proportion of children.…”

“…It is possible that secondary hydrocephalus destroys not only central regions of the CC, but also the AC and HC. However, the rate of enlargement of the AC has always been rather small even with complete agenesis produced by other disorders (Loeser & Alvord, 1968; Meyer et al, 1998; Rauch & Jenkins, 1994). …”