Radiculopathies

, Ali T. Ghouse² and Raghav Govindarajan³

(1)

Parkinson’s Clinic of Eastern Toronto and Movement Disorders Centre, Toronto, ON, Canada

(2)

McMaster University Department of Medicine, Hamilton, ON, Canada

(3)

Department of Neurology, University of Missouri, Columbia, MO, USA

Degenerative and traumatic spinal diseases commonly cause lesions of the cervical (CR) and lumbosacral (LR) nerve roots. Less often, vascular and inflammatory disorders can cause non-compressive nerve root lesions.

The most common clinical presentation in a radiculopathy is neck or back pain, arm or leg pain, or extremity paresthesia. Furthermore, there may be increased pain with coughing, sneezing, or the Valsalva maneuver, and reproduction of symptoms with a change in position, particularly for CR. Sensory symptoms consistent with injury to the sensory root fibers are numbness, pain, and paresthesia.

Electrodiagnostic (EDX) studies alone are capable of identifying physiological dysfunction, thus identifying ongoing injury to the nerve roots. This information may not be available through imaging studies. Further imaging studies cannot evaluate inflammatory or vascular nerve root damage.

Electrodiagnostic studies can demonstrate evidence of radiculopathy with both compressive and non-compressive etiologies. Although EDX studies are sensitive and specific for defining nerve root injury, EDX evaluation cannot determine the cause of the injury.

Bilateral studies are required to rule out a central disc herniation with bilateral radiculopathies, or spinal stenosis. The EDX evaluation needs to be extensive enough to develop the differential diagnosis of radiculopathy, plexopathies, polyneuropathies, or mononeuropathies—all of which can present with similar signs and symptoms.

Needle Electrode Examination

Needle electrode examination (NEE) is the single most useful procedure for the assessment of a nerve root lesion, as this examination assesses the physiological integrity of the root. The advantages of NEE for the evaluation of radiculopathy are that it identifies

abnormalities in myotome distribution, where multiple muscles innervated by the same spinal nerve root are involved, and these abnormalities can define root injury; NEE also
identifies the specific level or levels of a root injury and differentiates between root injury and other peripheral nerve lesions.
Defining the severity and duration of a root injury
When evaluating subclinical damage to the motor root that is evident with NEE but not evident from clinical manual muscle strength testing,

important considerations are that:

The NEE will be abnormal when the degree of the injury is sufficient to produce motor axon loss, conduction block, or both.
Such injury is not necessarily present in the motor fibers to all the muscles of a particular myotome.
To adequately screen each major myotome in the symptomatic limb, NEE of a sufficient number of muscles (five to seven), including the paraspinal muscles, is necessary.
Myotomal maps or charts may be used as a guide.
Fibrilation potential (FP) in a myotome distribution may be the only abnormality.
FP occurs in a proximal-to-distal sequence after the onset of a lesion.

NEE of paraspinal muscles is necessary for the proper assessment of radiculopathy.

Important considerations are:

FP in paraspinal muscles indicates axonal lesions in the posterior primary ramus, thus indicating axonal lesions within or near the neural foramina.
The multifidus is the deepest paraspinal muscle and is the only one considered to have monosegmental innervation.
FP in an acute root lesion may be found 6 or 7 days after the onset of the lesion, but may not appear in limb muscle for 5–6 weeks after the lesion onset.
FP and insertional positive sharp waves (PSW) occur in lumbar paraspinal muscles in 14.5 to 48 % of individuals.
Paraspinal FP may be found in radiculopathies, amyotrophic lateral sclerosis (ALS), focal trauma, metastasis, and myopathies, particularly in diabetes mellitus.
NEE may be suboptimal because of failure to achieve satisfactory muscle relaxation.
With NEE, the extensive overlap of root innervation makes it difficult to determine the specific root involvement.
NEE is of questionable value in the post-lumbar surgery period.