Pathological classification system of GM lesions in MS. GM lesion classification system as proposed by Bo et al,. 2003. Type 1 lesions (A) extend through both white and gray matter. Type 2 lesions (B) are intracortical, having no contact with white matter or with the surface of the brain. Type 3 lesions (C) extend inward from the surface of the brain. Type 4 lesions (D) extend through the whole width of the cortex without reaching into white matter. Reproduced from Geurts and Barkhof  with permission from Elsevier.
Hulst and Geurts BMC Neurology 2011 11:153 doi:10.1186/1471-2377-11-153