What does it mean if I have reduced lower leg reflexes before an Electromyography (EMG) test?

Reduced Lower Leg Reflexes Before EMG Testing

Reduced or absent lower leg reflexes (knee jerk/patellar reflexes) indicate dysfunction somewhere along the reflex arc—from the sensory nerve, through the spinal cord, to the motor nerve and muscle—and most commonly suggest a lower motor neuron problem, peripheral neuropathy, or neuromuscular disorder that your upcoming EMG will help characterize.

What Reduced Reflexes Mean

Diminished or absent deep tendon reflexes in the lower extremities can occur with several conditions 1:

• Lower motor neuron disorders (affecting the spinal cord motor neurons, nerve roots, or peripheral nerves)
• Peripheral neuropathies (such as Guillain-Barré syndrome, diabetic neuropathy, or polyneuropathy of critical illness) 1
• Neuromuscular junction disorders (like myasthenia gravis or botulism) 1
• Muscle diseases (myopathies) including muscular dystrophies 1
• Nerve root compression from spinal pathology 1

The absence of reflexes is particularly significant because it helps localize the problem to the peripheral nervous system rather than the brain or upper motor neurons (which typically cause increased reflexes) 1.

What the EMG Will Evaluate

Your EMG study will systematically assess where the problem lies 1, 2:

• Nerve conduction studies (NCS) will measure how well electrical signals travel through your nerves, identifying demyelinating conditions (like Guillain-Barré syndrome) where signals slow down, or axonal damage where signal amplitudes decrease 1
• Electromyography (needle EMG) will record electrical activity directly from your muscles to detect denervation (muscle fibers disconnected from their nerves), reinnervation patterns, or primary muscle disease 1
• Repetitive nerve stimulation may be performed if a neuromuscular junction disorder is suspected 1, 2

Important Context About Timing

The timing of your EMG is crucial for accurate diagnosis 1:

• Early in many disease processes (within the first 7-14 days), EMG findings may be normal or nearly normal even when reflexes are already diminished 1
• Wallerian degeneration (breakdown of damaged nerve fibers) takes approximately 7 days to become detectable on EMG 1
• If your symptoms are very recent, the EMG may need to be repeated in 2-4 weeks for complete diagnostic information 1

What to Expect During the Test

The EMG examination can take up to 2 hours and involves two components 1:

• Surface electrode testing for nerve conduction studies (electrical stimulation of nerves with recording from muscles)
• Needle electrode insertion into muscles to record electrical activity at rest and during contraction 1

The test can be uncomfortable, particularly the repetitive nerve stimulation portions, but provides critical functional information about your peripheral nervous system that imaging studies cannot reveal 1, 2.

Critical Red Flags

Seek immediate medical attention before your scheduled EMG if you develop 1:

• Rapidly progressive weakness ascending from legs to arms or affecting breathing
• Difficulty swallowing, double vision, or drooping eyelids (suggesting possible neuromuscular junction disorder)
• Severe pain, numbness, or loss of bowel/bladder control (suggesting possible spinal cord compression)
• Facial weakness or difficulty speaking (suggesting possible cranial nerve involvement)

Next Steps After EMG

The EMG results must be interpreted in conjunction with your clinical history, physical examination findings, and may require additional testing 1, 2:

• If neuropathy is confirmed, blood tests for diabetes, vitamin deficiencies, autoimmune conditions, or toxic exposures may be needed
• If myopathy is suspected, muscle enzyme levels (particularly creatine kinase) and possibly muscle biopsy may be indicated 1
• If neuromuscular junction disorder is found, specific antibody testing and possibly Tensilon testing may follow 1
• If nerve root compression is identified, MRI of the spine will likely be recommended 1

The combination of your reduced reflexes and the EMG findings will guide your physician toward the correct diagnosis and appropriate treatment plan 2.