Some science behind the scenes

Corpus Callosum and bipolar disorder

The corpus callosum is a wide, flat bundle of neural fibers beneath the cortex in the brain at the longitudinal fissure. It connects the left and right cerebral hemispheres and facilitates interhemispheric communication.

Reduced genual corpus callosal white matter integrity in pathological gambling and its relationship to alcohol abuse or dependence. - Yip SW et al; Division of Substance Abuse, Department of Psychiatry, Yale University School of Medicine, Connecticut Mental Health Center, New Haven, CT, USA.

Magnetic resonance imaging (MRI) studies have demonstrated functional prefrontal cortical (PFC) abnormalities in pathological gambling (PG) and other psychiatric disorders characterized by impaired impulse control; e.g., cocaine dependence and bipolar disorder.

These abnormalities are accompanied by impairments in white matter microstructures in the anterior (genual) corpus callosum (CC) in cocaine dependence and bipolar disorder.

So here we have the ultimate cause of manic depression– the corpus callosum is damaged,  and the Will  - trying to balance and invoke the functions of the two halves of the brain  - finds it cannot,  so instead it invokes those functions that can be stimulated, so one half of the brain gets hyperactivated – then the other.

The causes of this damage in turn also seem to vary.  Fetal damage seems to be yet again high on the agenda with genetic damage causing abnormal growth.  Once the gene controlling the growth has been damaged then the condition becomes hereditary.

This damage often shows up, as it does with schizophrenics in the malformation of the ventricular area.

Clinical correlates of lateral ventricular enlargement in bipolar affective disorder. - Pearlson GD, Garbacz DJ, Tompkins RH, Ahn HS, Gutterman DF, Veroff AE, DePaulo JR.

The presence of lateral ventricular enlargement in some manic-depressive subjects, as assessed by ventricular-brain ratios (VBRs), has been reported. A study of 27 bipolar patients and 27 individually matched normal controls confirmed that finding. Bipolar patients had significantly larger VBRs than did controls. Clinical measures associated with the presence of ventricular enlargement in the bipolar patients included more frequent hospitalizations and histories of persistent unemployment. Other measures of illness severity or social deterioration were not significantly associated with large VBR.

Pituitary volume and third ventricle width in euthymic patients with bipolar disorder. - Cousins DA et al; Newcastle Magnetic Resonance Centre, Newcastle University, Newcastle upon Tyne, United Kingdom.

Many of the clinical and neuroendocrine features of bipolar disorder involve hypothalamic structures. Although current neuroimaging techniques inadequately resolve the structural components of the hypothalamus, evidence of derangement can be sought by examining the adjacent third ventricle and the functionally related pituitary.

Euthymic adult patients with bipolar disorder (n=49) were compared with matched normal control subjects (n=47). Pituitary volume and third ventricle width were assessed on MRI scans. Basal salivary cortisol levels were measured.

Note: Euthymia is used in this context to refer to the neutral mood (absence of a depressive or manic cycle) that some people with bipolar disorder.

The width of the third ventricle in patients with bipolar disorder exceeded that of controls, with the greatest differences found in males.  Third ventricle width increased with age across the groups.

Studies into twins have been limited by relatively small sample sizes  - there are not many twins born with manic depressive parents, or born manic depressive, but those studies that have been carried out have indicated a “substantial genetic contribution”.

Although the first genetic linkage finding for mania was in 1969, the linkage studies have been inconsistent. There is not a manic depressive gene. The damage is done in the womb.