The Medical Research Council system

Motor recovery		Sensory recovery
M0	No muscle contraction	S0	No sensibility in the autonomous area
M1	Return of perceptible contraction in the proximal muscles	S1/S1+	Recovery of deep cutaneous pain sensibility/recovery of superficial cutaneous pain sensibility
M2	Return of perceptible contraction in the proximal and distal muscles	S2/S2+	Recovery of superficial cutaneous pain and some tactile sensibility/plus some overresponse
M3	Return of function in the proximal and distal muscles such that all important muscles can work against resistance	S3/S3+	Recovery of pain and tactile sensibility with disappearance of overresponse/plus recovery of some two point discrimination
M4	All muscles can work against resistance, and some independent movements are possible	S4	Full recovery of sensibility
M5	Full recovery of all muscle function

Adapted from:

Birch R, Bonney G, Wynn Parry CB. Results. In: Surgical Disorders of the Peripheral Nerves, 1st ed, Birch R, Bonney G, Wynn Parry CB (Eds), Churchill Livingstone, London 1998.
Lee SK, Wolfe SW. Peripheral nerve injury and repair. J Am Acad Orthop Surg 2000; 8:243.
Bagheri SC, Meyer RA, Khan HA, et al. Retrospective review of microsurgical repair of 222 lingual nerve injuries. J Oral Maxillofac Surg 2010; 68:715.
He B, Zhu ZW, Zhu QT, et al. Factors predicting sensory and motor recovery after the repair of upper limb peripheral nerve injuries. Neural Regen Res 2014; 9:661.

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