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Assessment of suspected motor neuron disease

BMJ 2022; 379 doi: (Published 23 November 2022) Cite this as: BMJ 2022;379:e073857
  1. Colin J Mahoney, consultant neurologist1,
  2. Richard Sleeman, freelance journalist and person living with motor neuron disease2,
  3. Will Errington, general practitioner3
  1. 1Forefront Motor Neuron Disease Clinic, Brain and Mind Centre, University of Sydney, Australia
  2. 2Sydney, Australia
  3. 3Rose Bay Family Medical Centre, Sydney, Australia
  1. Correspondence to C J Mahoney colin.mahoney{at}

What you need to know

  • Amyotrophic lateral sclerosis (ALS, a form of motor neuron disease) was previously considered rare, but incidence is expected to increase by 30% by 2040

  • ALS is a multisystem disease that commonly causes cognitive and behavioural changes; up to one quarter of patients meet the criteria for dementia

  • Diagnostic delay may reduce access to treatment and support that could improve survival and quality of life; refer urgently for expert assessment patients with asymmetrical painless progressive weakness or unexplained changes to swallowing

Motor neuron disease (MND) represents a group of neurodegenerative disorders that feature progressive motor weakness of limb or bulbar muscles (ie, those innervated by the lower brain stem). Classically, three distinct MND phenotypes are described, and these present along a spectrum of upper and lower motor neuron dysfunction,1 with increasing recognition of non-motor features.2

Amyotrophic lateral sclerosis (ALS) represents 85% of all MND cases, and features a combination of upper and lower motor neuron dysfunction.1 Primary lateral sclerosis (PLS) presents with upper motor neuron dysfunction, with substantial muscle spasticity. Primary muscular atrophy (PMA) presents with lower motor neuron dysfunction, with flaccid weakness and muscle atrophy. ALS is typically associated with rapid clinical decline, with survival typically 3-4 years from symptom onset, but PMA and more so PLS are associated with longer survival.3 This article focuses primarily on ALS.

Why should non-neurologists know about ALS?

People with ALS often experience challenges in getting the right diagnosis (box 1). Most patients visit their general practitioner first, typically with mild symptoms such as cramps, balance disturbance, reduced dexterity, or subtle cognitive changes including apathy. The time from symptom onset to diagnosis ranges from 10 to 16 months, and signs often go unrecognised, with patients referred to other specialists, or given misdiagnoses.5 Despite attempts to improve awareness in primary care, many doctors remain unfamiliar with …

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