FMGE 2011 — Pathology

Question 1: Diffuse axonal injury is characterized by lesion at:

• A. Basal ganglia
• B. Corpus callosum
• C. White matter
• D. Junction of gray and white matter (Correct Answer)

Explanation: ***Junction of gray and white matter*** - Diffuse axonal injury (DAI) is characteristically located at the **gray-white matter junction** (interface between cortex and subcortical white matter) [1] - The differential density and movement between gray and white matter during **rotational acceleration-deceleration injuries** creates maximum shearing forces at this junction [1] - This is the **classic and most characteristic location** of DAI lesions, particularly in the **parasagittal white matter** of cerebral hemispheres - Other common sites include corpus callosum and dorsolateral brainstem, but the gray-white junction is the hallmark location *White matter* - While DAI does involve damage to white matter tracts and axons, simply stating "white matter" is too non-specific [1] - Many other conditions affect white matter (demyelination, ischemia, etc.) - The **distinguishing feature of DAI** is its predilection for the gray-white interface, not white matter in general *Corpus callosum* - The corpus callosum is indeed a common site for **visible macroscopic DAI lesions** and hemorrhages [1] - However, this is just one specific location rather than the characteristic pattern - DAI is more broadly characterized by lesions at gray-white junctions throughout the brain *Basal ganglia* - The basal ganglia are deep gray matter structures not typically involved in classic DAI - These structures may be affected by other traumatic injuries like **contusions** or **deep hemorrhages** - DAI predominantly affects the interface zones and white matter tracts, not deep gray matter nuclei **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1262-1264.