This occurs in younger patients and shows a rapid progression. It is uncommon and affects the cerebral white matter more diffusely although the majority of cases show localised plaques in addition. Some cases show evidence of dysmyelination (abnormal myelin formation, as a result of biochemical defects) rather than demyelination and these cases exhibit similarities to sudanophilic leucodystrophy ( see later script).

Figure 4 is section of occipital lobe stained for myelin. The central white matter is pale due to lack of myelin.

This is rare and shows concentric rings of demyelination separated by bands of preserved myelin within the white matter.

This is uncommon and presents with plaques of demyelination within the spinal cord and optic nerves. The lesions may become necrotic ( break down as a result of tissue damage). Optic neuritis and spinal cord involvement usually occur within weeks of each other. Approximately two thirds of patients present with visual loss but in some cases spinal cord involvement occurs before involvement of the optic nerve. If the patient survives long enough they may develop other lesions characteristic of multiple sclerosis.