Quo vadis motor neuron disease?

Table 2 Motor neuron disease subtypes, discriminating features and possible differential diagnoses

MND subtype	Clinical features	Possible differential diagnoses
ALS	Affect both upper MNs and lower MNs	Cervical myeloneuropathy
	Onset 50 or 60 s	HIV
	Median survival 3 to 5 yr
PLS	Only affect upper MNs 3 yr from onset	Cervical myelopathy
	Onset 50 s	Nutritional (B12 or Cu deficiency)
	Profound spasticity	Primary progressive multiple sclerosis
	Progressive quadriparesis	Hereditary spastic paraparesis
	Late cranial nerve involvement	Stiff person syndrome
	Rarely bulbar onset	Tropical spastic paraparesis (HTLV1)
	Slow progression	Adrenomyeloneuropathy
	Median survival 5 to 10 yr	Hexosaminidase A deficiency
		Corticobasal degeneration
PMA	Only affect upper MNs 3 yr from onset	Benign fasciculations
	Focal asymmetric distal weakness, followed by proximal involvement	Post-polio syndrome
	Late bullar/respiratory involvement	Adult onset spinal muscular atrophy
	Earlier onset than ALS	Inclusion body myositis
	Raised CK (< 10 × normal)
	Median survival 3 to 5 yr

HIV: Human immunodeficiency virus; Cu: Copper; CK: Creatinine kinase; ALS: Amyotrophic lateral sclerosis; PLS: Primary lateral sclerosis; HTLV: Human T-cell lymphotropic virus; PMA: Progressive muscular atrophy.