Symptom Finder - Hypoactive Reflexes
HYPOACTIVE REFLEXES
Diffuse hypoactive reflexes are of no significance in otherwise healthy individuals; however, anatomy is the key to recalling the many pathologic causes of hypoactive reflexes. Visualizing the reflex arc , we have the spinal cord nerve roots, peripheral nerves, myoneural junction, and muscle. Now we simply think of the various diseases that may affect each one of these structures and we have an extensive list of possibilities.
Spinal cord: Diminished reflexes are seen in poliomyelitis, syringomyelia, Werdnig–Hoffman syndrome, muscular atrophy, and pernicious anemia with subacute combined degeneration. Spinal cord concussion, transection, or hemorrhage may cause hypoactive reflexes at first.
Nerve roots: Diffusely hypoactive reflexes may be found in Guillain– Barré syndrome and tabes dorsalis, both of which affect the nerve roots. Focal loss of reflexes may occur in herniated disc, cauda equina tumor, spinal stenosis, abscess, TB, multiple myeloma, and fracture.
Peripheral nerves: Peripheral neuropathy is associated with diffuse hypoactive reflexes. There are several causes including alcoholism, diabetes, drugs, malnutrition, Charcot–Marie–Tooth disease, porphyria, hereditary hypertrophic neuritis, lead intoxication, and collagen disease. Focal involvement may be seen in brachial plexus neuritis, sciatic
neuritis, and mononeuritis multiplex.
Myoneural junction: This should bring to mind myasthenia gravis.
Muscle: Generalized decrease in reflexes may be seen in dermatomyositis, advanced muscular dystrophy, myotonic dystrophica, and McArdle syndrome.
Approach to the Diagnosis
The differential diagnosis will depend on the presence or absence of other signs. If there is an acute onset of diffuse hypoactive reflexes and weakness, poliomyelitis Guillain–Barré syndrome, toxic peripheral neuropathy, and polymyositis must be considered in the differential diagnosis.
A gradual onset of diffuse weakness and hypoactive reflexes is more consistent with muscular atrophy, tabes dorsalis, pernicious anemia, and muscular dystrophy. Abnormal sensory findings would point to pernicious anemia, tabes dorsalis, and peripheral neuropathy whereas the absence of abnormal sensory findings would suggest muscular atrophy, muscular dystrophy, or myasthenia gravis. Focal loss of reflexes suggests a
herniated disc, especially if there is associated radicular pain. Focal hypoactive reflexes of the lower extremities require plain films of the lumbosacral spine, EMG and NCV studies, and an MRI or CT scan of the lumbar spine. Isolated hypoactive reflexes in the upper extremities require an x-ray of the cervical spine, MRI of the cervical spine, and NCV and EMG of the upper extremities. Diffuse hypoactive reflexes merit an extensive laboratory workup including a CBC, urinalysis, chemistry panel, serum B12 and folic acid, ANA, glucose tolerance test, blood lead level, urine for porphobilinogen, human immunodeficiency virus (HIV) antibody titer, and serum protein electrophoresis. A spinal tap should be done if Guillain–Barré syndrome is suspected. An EMG and NCV study should also be done if peripheral neuropathy or muscular dystrophy is suspected. A muscle biopsy may be needed in muscular dystrophy and dermatomyositis.
Other Useful Tests
1. Anti–double-stranded DNA (lupus)
2. Thyroid profile (hypothyroidism)
3. Immunoelectrophoresis (macroglobulinemia)
4. Kveim test (sarcoidosis)
5. Drug screen (drug-induced neuropathy)
6. Quantitative urine niacin and thiamine (pellagra, beriberi)
Diffuse hypoactive reflexes are of no significance in otherwise healthy individuals; however, anatomy is the key to recalling the many pathologic causes of hypoactive reflexes. Visualizing the reflex arc , we have the spinal cord nerve roots, peripheral nerves, myoneural junction, and muscle. Now we simply think of the various diseases that may affect each one of these structures and we have an extensive list of possibilities.
Spinal cord: Diminished reflexes are seen in poliomyelitis, syringomyelia, Werdnig–Hoffman syndrome, muscular atrophy, and pernicious anemia with subacute combined degeneration. Spinal cord concussion, transection, or hemorrhage may cause hypoactive reflexes at first.
Nerve roots: Diffusely hypoactive reflexes may be found in Guillain– Barré syndrome and tabes dorsalis, both of which affect the nerve roots. Focal loss of reflexes may occur in herniated disc, cauda equina tumor, spinal stenosis, abscess, TB, multiple myeloma, and fracture.
Peripheral nerves: Peripheral neuropathy is associated with diffuse hypoactive reflexes. There are several causes including alcoholism, diabetes, drugs, malnutrition, Charcot–Marie–Tooth disease, porphyria, hereditary hypertrophic neuritis, lead intoxication, and collagen disease. Focal involvement may be seen in brachial plexus neuritis, sciatic
neuritis, and mononeuritis multiplex.
Myoneural junction: This should bring to mind myasthenia gravis.
Muscle: Generalized decrease in reflexes may be seen in dermatomyositis, advanced muscular dystrophy, myotonic dystrophica, and McArdle syndrome.
Approach to the Diagnosis
The differential diagnosis will depend on the presence or absence of other signs. If there is an acute onset of diffuse hypoactive reflexes and weakness, poliomyelitis Guillain–Barré syndrome, toxic peripheral neuropathy, and polymyositis must be considered in the differential diagnosis.
A gradual onset of diffuse weakness and hypoactive reflexes is more consistent with muscular atrophy, tabes dorsalis, pernicious anemia, and muscular dystrophy. Abnormal sensory findings would point to pernicious anemia, tabes dorsalis, and peripheral neuropathy whereas the absence of abnormal sensory findings would suggest muscular atrophy, muscular dystrophy, or myasthenia gravis. Focal loss of reflexes suggests a
herniated disc, especially if there is associated radicular pain. Focal hypoactive reflexes of the lower extremities require plain films of the lumbosacral spine, EMG and NCV studies, and an MRI or CT scan of the lumbar spine. Isolated hypoactive reflexes in the upper extremities require an x-ray of the cervical spine, MRI of the cervical spine, and NCV and EMG of the upper extremities. Diffuse hypoactive reflexes merit an extensive laboratory workup including a CBC, urinalysis, chemistry panel, serum B12 and folic acid, ANA, glucose tolerance test, blood lead level, urine for porphobilinogen, human immunodeficiency virus (HIV) antibody titer, and serum protein electrophoresis. A spinal tap should be done if Guillain–Barré syndrome is suspected. An EMG and NCV study should also be done if peripheral neuropathy or muscular dystrophy is suspected. A muscle biopsy may be needed in muscular dystrophy and dermatomyositis.
Other Useful Tests
1. Anti–double-stranded DNA (lupus)
2. Thyroid profile (hypothyroidism)
3. Immunoelectrophoresis (macroglobulinemia)
4. Kveim test (sarcoidosis)
5. Drug screen (drug-induced neuropathy)
6. Quantitative urine niacin and thiamine (pellagra, beriberi)