In acute cerebellar lesions such as hemorrhage or trauma, all the tendon reflexes may be absent for hours or days. After that they may be obtainable but temporarily depressed.
In the less acute lesion some tendon reflexes are pendular.
Ask the patient to sit well forward on the edge of the examining table. Strike the patellar tendon as usual.
The leg will extend at the knee, then flex, and then extend again three or four times, with a decreasing range each time. The braking action of the quadriceps antagonists (the hamstrings) does not dampen the response after the first contraction of the quadriceps.
Pendular reflexes are not an exclusive cerebellar sign and may be present in any hypotonic condition.
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