Table 3

Key scenarios when specific investigations have most value in suspected motor neurone disease. None of these investigations is mandatory and are always guided by the clinical features

InvestigationGreatest value
Serum creatine kinaseMyopathy suspected, and as a clue to alternative diagnosis when >1000 IU/l
Cerebrospinal fluid analysisInflammatory neuropathy suspected, and when white cell count or protein significantly are raised
Oligoclonal band detection where primary progressive multiple sclerosis or paraneoplastic disorder suspected clinically
Nerve conduction studiesSuspected multifocal motor or other inflammatory neuropathy, or whenever there are prominent sensory features
ElectromyographyDemonstration of occult denervation in apparently unaffected body territories, or when myopathy suspected clinically
MRI brainIsolated dysphagia without prominent dysarthria, or hemiparesis
MRI cervical spineLack of signs above the neck with mixed signs progressive limb weakness
MRI lumbar spineLMN-only syndrome affecting only legs
Muscle biopsyInclusion body myositis suspected clinically or neurophysiologically
  • LMN, lower motor neurone.