Hyperactive tendon reflexes in spastic multiple sclerosis: measures and mechanisms of action.
OBJECTIVE
To develop new measures of tendon reflexes and evaluate hyperactive reflexes in patients with spastic multiple sclerosis (MS).


METHODS
With the subject relaxed, a hand-held instrumented hammer was used to tap the patellar tendon and record the tapping force, while knee extension torque and quadriceps EMG were recorded isometrically as measures of the reflex response.


METHODS
Research laboratory in a rehabilitation hospital.


METHODS
Ten spastic MS and 14 healthy subjects.


METHODS
Tendon tapping force (designated as system input), reflex torque (as output), their dynamic relationship (characterized as system parameters tendon reflex gain, contraction rate, and reflex loop delay), Ashworth scale, and tendon reflex scale.


RESULTS
The system parameters provide more repeatable measures than do input or output parameters alone because they quantify the input and output simultaneously and dynamically. Compared with control subjects, MS patients had a significantly lower threshold in tapping force (p = .026), yet their evoked reflex torque was significantly higher (p = .033). Despite significant quadriceps weakness (p < .0001), MS patients had a significantly higher reflex gain (p = .0002) and contraction rate (p = .0002), and shorter reflex loop delay (p = .0046), indicating hyperexcitability of motoneurons and peripheral receptors, and indicating that relatively more of the muscle was activated reflexively, with greater recruitment of larger fast-twitch fibers. Both the reflex gain and rate measures correlated more closely with the Ashworth scale and tendon reflex scale than did the output measures, indicating their potential clinical value.


CONCLUSIONS
With appropriate simplification, the method may be used in clinical practice to quantify more precisely the tendon jerk than is currently feasible with standard clinical tests.
Zhang
L Q
LQ
Rehabilitation Institute of Chicago, and Department of Physical Medicine and Rehabilitation, Northwestern University, IL, USA.
Wang
G
G
Nishida
T
T
Xu
D
D
Sliwa
J A
JA
Rymer
W Z
WZ
D000328:Adult; D005260:Female; D006801:Humans; D007717:Knee / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000503:physiopathology* / Q000534:rehabilitation; D009128:Muscle Spasticity / Q000503:physiopathology; D011930:Reaction Time; D012026:Reflex, Stretch