Marchiafava-Bignami Disease Workup

Updated: Jun 27, 2017
  • Author: Cortney Lyford, MD; Chief Editor: Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS  more...
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Workup

Approach Considerations

Because many patients with Marchiafava-Bignami disease (MBD) present with stupor or coma and seizures, the initial laboratory investigations should include measurements of serum electrolyte and glucose levels, a complete blood count (CBC), and toxicology screening. Glucose and intravenous (IV) thiamine are frequently given in the emergency department immediately after blood is drawn.

A spinal tap often is needed and usually is performed after findings on a brain CT scan have excluded an intracranial mass or hemorrhage.

Electroencephalography

Electroencephalography is frequently performed to evaluate seizures. No electroencephalographic findings are specific for or characteristic of MBD. [22]

CT scanning

Findings on the initial CT scan may confirm the diagnosis of MBD. If callosal damage is mild, however, it may go unnoticed until the radiologist has carefully reviewed the CT scan. In some cases, the lesions may not be visible on the scan.

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MRI

MRI is currently the most sensitive diagnostic tool for MBD. [23, 24] Fast spin-echo, T2-weighted MRI scans show hyperintensity of the lesions due to edema and myelin damage.

Hypointensity on T1-weighted images is mainly related to a total loss of myelin, with replacement of the region by a cyst. The “sandwich sign” is pathoneumonic for MBD and is seen on T1 weighted images as hypointensity in the central layers of the corpus callosum with sparing of the dorsal and ventral layers. Neurons can also be lost, in a situation similar to that of multiple sclerosis. As reported by Sair et al., diffusion tensor imaging and the associated technique of fiber tracking can further increase the sensitivity of MRI. [25]

Sagittal fluid attenuation and inversion recovery Sagittal fluid attenuation and inversion recovery image displaying central hypointensity (suggesting cavitation) with surrounding hyperintense rim (active inflammation) (white arrowheads) involving the genu, body, and splenium of corpus callosum. Courtesy of Case Reports in Radiology, Hindawi Publishing Corp.

Acute or subacute lesions are characterized by edema and early myelin damage more than other changes. As lesions become chronic, cystic lesions are likely to develop. Cystic lesions are generally hyperintense around the rim on T2-weighted MRI scans and hypointense in the actual cavity on T1-weighted images.

T2-weighted axial image in a patient with Marchiaf T2-weighted axial image in a patient with Marchiafava-Bignami disease showing a high-signal lesion in the corpus callosum.

Fluid-attenuated inversion recovery (FLAIR) images may be even more sensitive than those described above. Hyperintense rims and hypointense cores on FLAIR images probably represent damage to the myelin at the rim, with a central necrotic area. Uniformly hyperintense lesions may contain a mixture of demyelination and edema. In acute lesions, the area of edema seen is frequently larger than the area of permanent damage.

Pathology may also be seen on diffusion-weighted imaging. Unlike in stroke, however, in MBD, according to a report by Hlaihel et al, it is not uncommon for areas of restricted diffusion to resolve completely without apparent permanent damage. [20, 26]

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Histologic Findings

Degeneration of the corpus callosum is a cardinal feature of MBD. The middle portion (middle lamina) of the myelinated fiber tracts of the corpus callosum degenerates. The degeneration is frequently, but not always, uniform. In some cases, the anterior portion is preferentially involved, with the most severe degeneration in the center of the lesion.

The anterior and posterior commissures, the centrum semiovale, the brachium pontis, and the other white-matter tracts (eg, the long association fibers and the middle cerebral peduncles) may also be affected. However, the internal capsule and corona radiata, as well as the shorter arcuate subgyral association fibers, are typically spared. If the splenium of the corpus callosum is affected, the greatest degeneration most commonly occurs in the lateral portions of the middle segment.

Histopathologic studies reveal abundant macrophages in the areas of lesions. Otherwise, little inflammatory reaction is noted. Axons are demyelinated in the involved areas, but the axon cylinders are relatively spared, particularly in the peripheral portions of the lesions. Deep in the lesion, cavitation, or cyst formation may be seen and corresponds to complete necrosis of all neural and glial elements.

Patients with MBD do not usually have midline lesions, which are typical in patients with Wernicke-Korsakoff syndrome (of the medial thalamus or mamillary bodies).

Finally, as previously mentioned, cortical lesions are sometimes found on postmortem neuropathologic studies. In such cases, neuronal degeneration of the third and fourth layers of the frontal and temporal cortices has been found, with replacement of the neuron by gliosis (ie, Morel cortical laminar sclerosis).

Controversy exists as to whether cortical MRI findings in MBD actually correlate with such pathologic findings and whether they may have implications for prognosis. Whether the cortical findings are secondary to the callosal damage, whether both are caused by a similar process, or whether they are coincidental findings that may also occur separately, particularly in severe alcoholism, malnutrition, and/or other severe impairments, remains unclear.

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