In this case, with a severe sensory deficit, one would expect a diminished or absent reflex. If the problem is S1 radiculopathy, consideration should be given to what sort of lesion might permit a bolus of afferent impulses to cross the dorsal root and arrive at the spinal cord in a synchronous manner. Such a lesion would have to damage some afferent fibers severely while sparing totally a substantial number of others. This is not likely to happen as a result of a compressive lesion. The data collected so far do not suggest additional involvement in other areas, but a general screening neurologic examination is needed.
Cranial nerves are intact.
In the upper limbs, muscle bulk and tone are normal, and there is no weakness. Muscle stretch reflexes are present and symmetric bilaterally. No sensory abnormality is noted. If necessary, revise your differential diagnosis based on the additional physical findings. Design your approach to the electrophysiologic examination based on the existing data.