Demographic data of patient groups
| Group | n | Male/ female |
Age (mean SD) (y) |
| Normal controls | 18 | 9/9 | 34 (10) |
| Neurological controls: | |||
| Peripheral neuropathy | 3 | ||
| Motor neuron disease | 2 | ||
| Sciatica | 4 | ||
| Spinal stenosis | 2 | ||
| Back pain | 2 | ||
| Disc prolapse | 1 | ||
| Headache | 1 | ||
| Mechanical nerve root damage | 1 | ||
| Sleep disorder | 3 | ||
| Vertebrobasilar ischaemia | 1 | ||
| Total | 20 | 9/11 | 53 (15) |
| Depression | 46 | 19/27 | 53 (16) |