Table 3.

Qualitative data showing the effect of stimulation on the character of pain

Subject	Mechanism of injury	Pain quality	PAG effect	CmPf effect
1	Diagnostic glycerol injection into the trigeminal nerve ganglion performed with no relief of symptoms and complicated by a loss of sensation to V1, V2, and V3 dermatomes	Constant burning pain; reduced sensation and paraesthesia over V1, V2, and V3 dermatomes; pain increased by noise	Skin feels less tight; reduction in pins and needles; can tolerate wind on face	Face pain duller; cheek feels the same pain but perceived as less unpleasant
2	Assaulted in 2005, sustaining multiple facial stab wounds from a screwdriver; a fracture through his left zygoma resulted in a unilateral loss of facial sensation and taste; an MRI demonstrated no vascular compression of the trigeminal nerve ganglion, only a cyst-like lesion (which may have been a neuroma) in the left maxillary sinus, which was surgically excised; subsequent to this operation his facial pain worsened acutely	Continuous throbbing, aching pain like something very hot or cold is running across the cheek; paroxysmal shooting pains within the maxillary branch (V2) of the trigeminal nerve; shooting pain triggered by cold air, laughing, talking, and eating; severe allodynia over V2 dermatome	Reduction in frequency of shooting pains and relief from aching pain	Skin feels numb; less sensitive to wind on face; dizzy for 30 s when first switched on
3	Diagnosed with trigeminal neuralgia; MRI confirmed vascular compression, and microvascular decompression alleviated her symptoms for 6 weeks before the pain returned; a partial sensory rhizotomy was performed which qualitatively altered the characteristics of her pain in keeping with the development of anaesthesia dolorosa	Tingling in cheek present 90% of time; burning and shooting pains triggered by radiant heat or cold air, talking, and hot drinks; increased sensitivity with noise	Slight warm sensation across face; reduced sensitivity to cold air	Patient described having a ‘comfortable’ pain: ‘it is still there but I can tolerate it and it doesn't seem to affect me so much’; tingling over face; reduced allodynia to wind/touch