(C) C5 to T1 # Preganglionic lesions have a poor prognosis as these do not recover and are surgically irreparable.> Postganglionic lesions have better prognosis than preganglionic lesions and histamine test is useful in making the distinction> Postganglionic lesions: Disruption proximal to the dorsal root ganglion Avulsion of nerve root from the spinal cord Cannot Recover Surgically irreparable Histamine test is positive Pseudomeningoceles on CT myelography or MRI due to root avulsion may be seen (positive result is unreliable during first few days). Sensory conduction from anaesthetic dermatome on nerve conduction studies suggests a preganglionic lesion (i.e. nerve distal to ganglion is not interrupted)> Erb's palsy: Upper obstetric palsy C5-C6 roots are affected Abductors and external rotators of the shoulder are paralysed Arm is held to the side (adducted), internally rotated and pronated (Waiter's tip deformity)> Klumpke's palsy: Lower obstetric palsy C8-T1 roots are affected (Involvement of T1 root may cause a homer's syndrome due to sympathetic nerve disturbance) This is a complete plexus lesion and more severe. Arm is frail and pale. Generalized wasting of all intrinsic muscles and a claw hand deformity is seen. Unilateral (ipsilateral) Horner's syndrome is often associated.> Histamine test: Intradermal injection of histamine usually causes a triple response in the surrounding skin. Central capillary dilatation Wheel Surrounding flare> If the flare reaction persists in an anaesthetic area of skin, the lesion must be proximal to the posterior root ganglion i.e. it is probably a root avulsion.> Postganglionic lesions have better prognosis than preganglionic lesions and histamine test is useful in making the distinction.