The ataxia and recumbency that coincided with onset of analgesia might be due to diminished blockage of sensory sympathetic and motor fibre
by the drug.
Because sensory fibres are more sensitive to local anaesthetics than motor fibres
it is possible to block pain fibres selectively, without affecting motor fibres
, by using dilute concentrations of local anaesthetic.
Disruption of ipsilateral motor fibres
and associated motor weakness does not appear to be the cause of the sensory-motor deficit demonstrated.
are located more peripherally than sensory fibres.
Second, the diameter of median nerve is greater than ulnar, so with large diameter and few motor fibres
, scope of error in co potation is big, this is not true for ulnar nerve, as it leaves very little scope of error, with small diameter and large number of motor fibres