Demyelinating Disorders of the CNS

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Chapter 593 Demyelinating Disorders of the CNS

Demyelinating disorders of the central nervous system (CNS) cause acute or relapsing-remitting encephalopathy and other multifocal signs of brain, brainstem, and spinal cord dysfunction. They affect white matter, which is formed by myelin contained within oligodendrocytes, providing electrical insulation for neurons and neuronal connections. In contrast to genetically determined leukodystrophies (sometimes called dysmyelinating disorders) that also produce disrupted white matter, demyelinating disorders generally target normally formed white matter through immune-mediated mechanisms. Major demyelinating disorders in childhood include multiple sclerosis (MS) and acute disseminated encephalomyelitis (ADEM). The rare macrophage activating syndromes and isolated angiitis of the CNS can sometimes be confused with ADEM (Table 593-1).

Table 593-1 SUMMARY OF CONSENSUS DEFINITIONS FOR PEDIATRIC CENTRAL NERVOUS SYSTEM INFLAMMATORY DEMYELINATION

MONOPHASIC CNS INFLAMMATORY DEMYELINATION
ADEM Clinical event must include encephalopathy (behavioral change and/or altered consciousness)
New symptoms or signs within 3 months are considered part of same ADEM event
CIS Clinical event that can be monofocal (e.g., isolated optic neuritis) or polyfocal, but cannot include encephalopathy
NMO Must have optic neuritis and transverse myelitis as major criteria. Must have spinal MRI lesion extending over 3 or more segments or be NMO-IgG positive
RELAPSING CNS INFLAMMATORY DEMYELINATION
Recurrent ADEM New event of ADEM (must have encephalopathy) with recurrence of initial ADEM symptoms and signs 3 or more months after initial event and not related to withdrawal of steroids
Multiphasic ADEM ADEM followed by new clinical event also meeting criteria for ADEM, but involving new CNS lesions (clinically and radiologically)
Relapsing NMO Relapse of NMO as described above. Additional clinical and radiologic features extrinsic to optic nerve and spinal cord are well described and acceptable for diagnosis
Pediatric MS Two or more events separated in time (4 or more weeks) and space. First episode cannot be ADEM. If 1st episode is ADEM, 2 or more non-ADEM events are required for diagnosis of MS. New MRI lesions 3 months or longer after the initial clinical event can be used to satisfy criteria for dissemination in time

All events must include compatible MRI features of CNS inflammatory demyelination and exclude alternative causes.

ADEM, acute disseminated encephalomyelitis; CIS, clinically isolated syndrome; CNS, central nervous system; MS, multiple sclerosis; NMO, neuromyelitis optica.

(Data from Krupp LB, Banwell B, Tenembaum S: Consensus definitions proposed for pediatric multiple sclerosis and related disorders, Neurology 68[16 Suppl 2]:S7–S12, 2007.)

593.1 Multiple Sclerosis

Multiple sclerosis (MS) is a chronic demyelinating disorder of the brain, spinal cord and optic nerves characterized by a relapsing-remitting course of neurologic episodes separated in time and space.

Clinical Manifestations

Presenting symptoms in pediatric MS include hemiparesis or paraparesis, unilateral or bilateral optic neuritis, focal sensory loss, ataxia, diplopia, dysarthria, or bowel/bladder dysfunction (Table 593-2). Polyregional symptoms are reported in 30% of patients. Encephalopathy is less common and suggests consideration of acute disseminated encephalomyelitis (ADEM).

Table 593-2 SYMPTOMS AND SIGNS OF MULTIPLE SCLEROSIS BY SITE

  SYMPTOMS SIGNS
Cerebrum Cognitive impairment Deficits in attention, reasoning, and executive function (early); dementia (late)
Hemisensory and motor Upper motor neuron signs
Affective (mainly depression)  
Epilepsy (rare)  
Focal cortical deficits (rare)  
Optic nerve Unilateral painful loss of vision Scotoma, reduced visual acuity, color vision, and relative afferent papillary defect
Cerebellum and cerebellar pathways Tremor Postural and action tremor, dysarthria
Clumsiness and poor balance Limb incoordination and gait ataxia
Brainstem Diplopia, oscillopsia Nystagmus, internuclear and other complex ophthalmoplegias
Vertigo  
Impaired swallowing Dysarthria
Impaired speech and emotional lability Pseudobulbar palsy
Paroxysmal symptoms  
Spinal cord Weakness Upper motor neuron signs
Stiffness and painful spasms Spasticity
Bladder dysfunction  
Erectile impotence  
Constipation  
Other Pain  
Fatigue  
Temperature sensitivity and exercise intolerance  

Modified from Compston A, Coles A: Multiple sclerosis, Lancet 372:1502–1517, 2008, p 1503.