OBJECTIVE: To compare results of quantitative sudomotor axon reflex testing (QSART), dorsal sural, and sural sensory nerve testing in patients with painful sensory neuropathy (PSN). METHODS: Fifty-six patients with symptoms and neurologic examinations consistent with PSN who had both autonomic and nerve conduction studies were identified from 376 patients with a clinical diagnosis of painful neuropathy. Cases were clinically categorized as large-fiber or small-fiber neuropathies by described criteria. The results of sural, dorsal sural, and QSART tests were then analyzed in relationship to these two clinical groups. RESULTS: Evidence of unmyelinated fiber abnormalities by QSART was noted in 85% of clinical large-fiber and 69% of clinical small-fiber groups. Dorsal sural potentials were absent in all the large-fiber group but also in 52% of clinically classified small-fiber neuropathies. When QSART and dorsal sural abnormalities were combined, the identification of abnormalities in all the cases of PSN was 89% with 75% of cases (42) showing mixed large and small fiber abnormalities, 14% unmyelinated sensory fiber abnormalities (by QSART), and 11% normal studies. CONCLUSION: This study demonstrates the value of combining both QSART and dorsal sural sensory testing in verifying the diagnosis of PSN. The majority of cases demonstrate involvement of unmyelinated C fibers as well as large/medium myelinated fibers, thereby separating mixed large- and small-fiber sensory neuropathies from those cases classified by clinical criteria solely as small-fiber neuropathy.
OBJECTIVE: To compare results of quantitative sudomotor axon reflex testing (QSART), dorsal sural, and sural sensory nerve testing in patients with painful sensory neuropathy (PSN). METHODS: Fifty-six patients with symptoms and neurologic examinations consistent with PSN who had both autonomic and nerve conduction studies were identified from 376 patients with a clinical diagnosis of painful neuropathy. Cases were clinically categorized as large-fiber or small-fiber neuropathies by described criteria. The results of sural, dorsal sural, and QSART tests were then analyzed in relationship to these two clinical groups. RESULTS: Evidence of unmyelinated fiber abnormalities by QSART was noted in 85% of clinical large-fiber and 69% of clinical small-fiber groups. Dorsal sural potentials were absent in all the large-fiber group but also in 52% of clinically classified small-fiber neuropathies. When QSART and dorsal sural abnormalities were combined, the identification of abnormalities in all the cases of PSN was 89% with 75% of cases (42) showing mixed large and small fiber abnormalities, 14% unmyelinated sensory fiber abnormalities (by QSART), and 11% normal studies. CONCLUSION: This study demonstrates the value of combining both QSART and dorsal sural sensory testing in verifying the diagnosis of PSN. The majority of cases demonstrate involvement of unmyelinated C fibers as well as large/medium myelinated fibers, thereby separating mixed large- and small-fiber sensory neuropathies from those cases classified by clinical criteria solely as small-fiber neuropathy.