Tibialis anterior R-1 response: physiological behaviour, normative data and clinical utility in L4-L5 radicular compression

Clinical uses of H reflexes of upper and lower limb muscles

H reflexes can be recorded from virtually all muscles that have muscle spindles, but reflex reinforcement may be required for the reflex response to be demonstrable. This can allow conduction across proximal nerve segments and most nerve root segments commonly involved by pathology. Stimulus rate is critical in subjects who are at rest. However the reflex attenuation with higher rates is greatly reduced during a background contraction of the test muscle, with only minor changes in latency if any. In addition the contraction ensures that the reflex response occurs in the desired muscle. Reflex latencies should be corrected for height (or limb length) and age. Because the reflex discharge requires a synchronised volley in group Ia afferents, large increases in reflex latency occur rarely with purely sensory lesions. If the H reflex of soleus, quadriceps femoris or flexor carpi radialis is absent at rest but appears during a voluntary contraction at near-normal latency, there is either low central excitability or a predominantly sensory abnormality. With the former H reflexes will be difficult to elicit throughout the body. If H reflexes can be recorded at rest from muscles for which no reflex can normally be demonstrated, there is good evidence for hyperreflexia. In the context of possible ALS, this is an important finding when there is EMG evidence of chronic partial denervation in that muscle.

Contraction induced h reflexes in the diagnosis of cervical radiculopathy

PURPOSE

To determine whether Contraction Induced H Reflexes (CIHR) can accurately detect cervical radiculopathy.

METHODS

Comparison of CIHR results with Needle Electromyography at academic outpatient Electromyography/Nerve Conduction laboratories. Participants were all patients over 18 with a needle electromyography diagnosis of cervical radiculopathy. Patients were tested for CIHR in at least two upper extremity muscles in electromyographically proven myotomes bilaterally. Patients were requested to perform a moderate contraction while stimulus was applied proximally (elbow or Erb's point). Outcome measures included H Reflex onset latency and side-to-side latency differences. These were compared against previously established normal values.

RESULTS

Overall, 10 of 15 patients who met criteria for cervical radiculopathy showed CIHR abnormalities (sensitivity = 67%; 95% confidence interval, 43-91). Counting each side and level separately, CIHR identified 16/27 radiculopathies (sensitivity = 59.2%; 95% confidence interval, 40.6-77.8). Contraction Induced H Reflexes identified 1 possible radiculopathy not seen on electromyography (specificity = 98%; 95% confidence interval, 95-100).

CONCLUSIONS

Contraction induced H Reflexes have a sensitivity and specificity for cervical radiculopathy similar to the resting Gastroc-Soleus H Reflex.

Parainfectious conus myelitis

We describe electroclinical and imaging features of a peculiar type of parainfectious myelitis that selectively involves the conus/epiconus region of the spinal cord. Twelve patients of parainfectious myelitis with MRI evidence of inflammatory lesions in the conus/epiconus region of the spinal cord were studied. All patients underwent full clinical and electrophysiological evaluation along with MRI of the spine. MRI included axial images at the site of lesion. All patients had a unique clinical presentation with urinary symptoms. Careful clinical examination revealed minimal sensorimotor dysfunction in the lower lumbar and sacral segments, which remained unnoticed by most of the patients; three female patients had no sensorimotor deficit. The motor paralysis recorded in four patients was flaccid and areflexic. The sensory level was inconspicuous as it was in the leg area corresponding to the lumbar and sacral spinal segments. Sensory loss was significantly more in the perineal region in those seven patients who had MRI evidence of inflammatory lesion in conus medullaris; two patients had maximum sensory loss in lumbar dermatomal distribution, which corresponded with the focal segmental myelitis involving 'epiconus'. MRI done in the sagittal plane was either normal or only 'suggestive' of myelitis in most of the patients and the inflammatory lesions were much more visible in the axial plane. The lesions predominantly involved central gray matter with spread to adjoining white matter in nine patients; in three patients with pure bladder involvement, lesions were confined to lateral gray matter of the conus medullaris. Our findings indicate that parainfectious myelitis (PIM) selectively involving conus medullaris is an important cause of unexplained acute or sub-acute urinary symptoms in adolescent and adult patients. In suspected cases, MRI must include axial images of the conus-epiconus region, as sagittal images may not always reveal the lesion. Due to initial presentation with urinary symptoms, absent or minimal sensory-motor signs, no transverse level over the trunk and unique MRI features, this condition may be called parainfectious conus myelitis (PICM).