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
| Investigation | Greatest value |
|---|---|
| Serum creatine kinase | Myopathy suspected, and as a clue to alternative diagnosis when >1000 IU/l |
| Cerebrospinal fluid analysis | Inflammatory 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 studies | Suspected multifocal motor or other inflammatory neuropathy, or whenever there are prominent sensory features |
| Electromyography | Demonstration of occult denervation in apparently unaffected body territories, or when myopathy suspected clinically |
| MRI brain | Isolated dysphagia without prominent dysarthria, or hemiparesis |
| MRI cervical spine | Lack of signs above the neck with mixed signs progressive limb weakness |
| MRI lumbar spine | LMN-only syndrome affecting only legs |
| Muscle biopsy | Inclusion body myositis suspected clinically or neurophysiologically |
LMN, lower motor neurone.