RELATIVE PRESERVATION OF MEDIAN MOTOR FIBERS TO THE SECOND LUMBRICAL MUSCLE IN SEVERE CARPAL TUNNEL SYNDROME
Smith B.E., Stevens J.C. Mayo Clinic Scottsdale, Scottsdale, AZ
PROBLEM: Carpal tunnel syndrome (CTS) research often focuses on the earliest stages of disease. In severe CTS where routine median motor and palmar responses are absent, localization is less certain. Median nerve fibers innervating the 2nd lumbrical (M2L) muscle may be less affected by CTS. Comparison of the median distal motor latency (DML) recording from the M2L with the ulnar DML recording over the interossei (UI) has been described for diagnosis of CTS. METHODS: The EMG database of all patients studied at Mayo Clinic Scottsdale in 1997 and 1998 was queried for all CTS cases who showed absent median/ abductor pollicis brevis motor responses and absent median palmar responses who also underwent M2L/UI NCS. RESULTS: Nineteen CTS hands in 18 patients were identified. The gender ratio was 1:1. The mean age was 76 years. Of the 19 hands studied, 18 had a recordable M2L response (mean amplitude 0.5 mV, range 0.1-2.0) and all had UI responses (mean amplitude 5.3 mV, range 2.9-14.0). The mean M2L DML was 8.2 ms (range 3.9-13.7); the mean UI DML was 3.1 ms (range 2.4-3.7). The mean median to ulnar DML difference was 5.1 ms (range 0.6-10.5, normal <0.5 ms). CONCLUSION: In patients with electrophysiologically severe CTS in whom routine median motor and palmar responses are unobtainable, there is relative preservation of the median/2nd lumbrical response (17/18 patients, 94.4%). Increased difference between M2L, and UI DMLs is a reliable and robust NCS technique in the diagnosis of electrophysiologically severe CTS.
NEAR-NERVE STUDIES IN PATIENTS WITH PAINFUL NEUROPATHIES
Smith T., Sindrup S.H., Johannsen L. Odense University Hospital, Odense, Denmark.
Pain in polyneuropathy has been postulated as due to ephaptic
transmission between regenerating thinly myelinated sensory nerve
fibers. The objective of the present study was to find evidence
for regenerating sensory nerve fibers in painful polyneuropathies
of different etiology. We studied 57 consecutive patients with
polyneuropathy using sensory near-nerve technique. The presence
of an axonal polyneuropathy was documented by clinical findings
and sensory and motor conduction studies. The patients were included
in one of three groups of painful polyneuropathies: Diabetic,
alcoholic and others, and compared with each other and a fourth
group of patients with polyneuropathies without pain. Near-nerve
conduction studies were performed on the median and sural nerves
using needle electrodes for recording and averaging 500-1000 responses.
The minimal conduction velocity was calculated using the slowest
response which was clearly separated from the background. In the
median nerve study the minimal conduction velocity (mean m/s ±
standard deviation) was 15 ± 5.8 in the diabetic group,
14 ± 4.5 in the alcoholic group, 15 ± 5.6 in the
group of others with pain, and 16 ± 5.3 in patients without
pain. In the sural nerve study the results were 14 ± 4.9
in the diabetics, 14 ± 4.5 in the alcoholics, 12 ±
4.3 in the group of others with pain, and 13 ± 6.0 in patients
without pain. There was no significant statistical difference
between groups and no difference between groups and normals. It
is concluded that painful neuropathy seems not to be associated
with regenerating slowly conducting sensory nerve fibers in the
range studied by near-nerve technique. These fibers may not be
involved in pain sensation.
VISUAL EVOKED POTENTIAL STUDY IN CHRONIC INFLAMMATORY DEMYELINATING POLYNEUROPATHY
Stojkovic T.(1) , de Seze J.(1), Hurtevent J.F.(2) , Beaume A.(4), Arndt C.(3), Hache J.C.(3), Vermersch R.(1) Departments of Neurology(1), Neurophysiology(2), Neuroopthalmology(3), University of Lille, France. Department of Immunology(4), University of Poitiers, France
BACKGROUND: The frequency of the association between chronic demyelinating inflammatory polyneuropathy (CIDP) and central nervous system (CNS) demyelinating lesions is probably underestimated (Uncini et al., 1996). OBJECTIVE: To investigate the occurrence of combined central and peripheral demyelination in CIDP patients and to correlate visual evoked potentials (VEP) abnormalities with brain magnetic resonance imaging (MRI) and antibodies to gangliosides. PATIENTS AND METHODS: Nerve conduction studies (NCV), VEP and dosage of antibody to gangliosides were evaluated in 17 patients with CIDP. Brain MRI was performed in patients with abnormal VEP. RESULTS: The seventeen patients fulfilled the diagnostic criteria outlined for CIDP (Cornblath et al., 1991). Latency of VEP was increased in 8 CIDP patients. Among these patients, brain MRI showed demyelinating lesions in 4 patients, aged from 17 to 65 years. One of these patients had antibodies to SGLPG. Antibodies to GM1 was found in one patient who had normal VEP. CONCLUSION: This study confirms the high frequency of abnormal VEP in CIDP, which are poorly correlated with CNS demyelinating lesions and antibodies to gangliosides. Abnormalities in VEP may be explained by the susceptibility to immune-mediated damage of both peripheral and optic nerve.
OTOTOXICITY IN EXPERIMENTAL CISPLATIN NEUROPATHY
Dondè E., Tredici P., Fagnani E., Cavaletti G.(1), Tredici G.(2) ENT Dept, IRCCS Ospedale Maggiore Policlinico, Milano, (1)Fifth Dept of Neurology, Ospedale San Gerardo, Monza, (2)Inst. Human Anatomy, Segrate, University of Milan, Italy.
Repeated administrations of cisplatin induce a sensory ganglionopathy in rats. To assess the ototoxicity and regenerative capabilities of cochlear hair cells, 7 Wistar rats were treated with i.p. cisplatin (2 mg/Kg) twice a week for 9 administrations. Cochlear function was evaluated by means of electrocochleography using an Amplaid MK 22, upon anesthesia with ketamine. Electrocochleography was recorded from the right side using alternating clicks and a wide filter setting. The stimulus intensity was 100 dB SPL. Five hundred samples were averaged. Auditory brainstem responses were also determined. Determinations were performed before treatment, at week 5 (at the end of cisplatin treatment), and after 10 and 15 weeks. At week 5, there was a significant increase of NI and N2 peak latencies respect to the pre-treatment values, which was less evident at 10 and 15 weeks. After treatment the typical morphology of the electrocochleography was lost and the amplitude of the waves was reduced. At 10 and 15 weeks the latencies were shorter than at week 5 but they were still prolonged. Amplitude and morphology of N1 and N2 peak were also recovering. No differences were observed between determinations at week 10 and 15. Auditory brainstem responses remained unchanged at all determinations. The study demonstrates that cisplatin ototoxicity in rats is limited to the cochlear hair cells without involvement of the auditory nerve and of the central auditory pathways in accordance with human findings. Moreover, recovery in electrocochleography demonstrates that the hair cell damage is partially reversible indicating regenerative capabilities of the cochlear epithelium.
THE EFFECT OF ANALGESICS ON QUANTITATIVE SENSATION TEST THRESHOLDS
Wang A., Gillen D.A., and Dyck P.J. Mayo Clinic, Rochester, MN, USA
BACKGROUND: QST is increasingly being used to characterize
disease alterations in epidemiological studies and as an endpoint
in controlled clinical trails. The effect of analgesics on QST
results in normal subjects has not been adequately studied. OBJECTIVE:
To determine whether commonly used analgesics affect quantitative
sensation test (QST) results and whether they should be withheld
prior to testing. MATERIAL AND METHODS: Subjects: Twenty
healthy subjects with normal neurologic examinations were selected.
Subjects who had an underlying neurologic disorder or conditions
that would predispose to neuropathy, or who were taking medications
that might affect sensory thresholds, were excluded. STUDY DESIGN:
A double-blind, placebo-controlled randomized study was done.
Subjects underwent QST before and after treatment with placebo,
aspirin, acetaminophen and acetaminophen with codeine. RESULTS:
No significant difference was found between mean baseline
and placebo QST results. Mean cooling detection thresholds were
increased compared to baseline after aspirin (p=0.006) and acetaminophen
(p=0.006). However, the mean change in QST after treatment (baseline
minus treatment QST) did not show a significant difference when
compared to the change in QST after placebo (baseline minus placebo
QST). CONCLUSION: Single doses of commonly used analgesics do
not appear to have a large effect on QST results and probably
do not need to be withheld prior to testing.