Impaired sensation to pinpick only may consistent with a small fiber neuropathy, which would have normal NCS/EMG findings. 

Quantiative sudomotor axon testing (QSART), which evaluates postganglionic sympathetic sudomotor axons, measures the autonomic nerves that control sweating. 

~75% of patients with a distal small fiber neuropathy will have an abnormal QSART