Return to spinal pain home pageBack and Neck Pain part-2

 

Table 16-1: Lumbosacral Radiculopathy-Neurologic Features

Examination Findings         Lumbosacral Nerve Roots Reflex Sensory Motor Pain Distribution   Lumbar-2 or L2 - Upper anterior thigh Psoas (hip flexion) Anterior thigh   L3a - Lower anterior thigh Anterior knee Psoas (hip flexion) Quadriceps (knee extension) Thigh adduction Anterior thigh, knee   L4a Quadriceps (knee) Medial calf Quadriceps (knee extension)b Thigh adduction Tibialis anterior (foot dorsiflexion) Knee, medial calf   L5c - Dorsal surface-foot Lateral calf Peroneii (foot eversion)b Tibialis anterior (foot dorsiflexion) Gluteus medius (hip abduction) Toe dorsiflexors Lateral calf, dorsal foot, posterolateral thigh, buttocks   S1c Gastrocnemius/soleus (ankle) Plantar surface-foot Lateral aspect-foot Gastrocnemius/soleus (foot plantar flexion)b Abductor hallucis (toe flexors)b Gluteus maximus (hip extension) Bottom foot, posterior calf, posterior thigh, buttocks aReverse straight leg-raising sign present-see 'Examination of the Back.' bThese muscles receive the majority of innervation from this root. cStraight leg-raising sign present-see 'Examination of the Back.'

Laboratory Studies

Routine laboratory studies such as a complete blood count, erythrocyte sedimentation rate, chemistry panel, and urinalysis are rarely needed for the initial evaluation of acute (<3 months), nonspecific, low back pain. If risk factors for a serious underlying disease are present, then laboratory studies (guided by the history and examination) are indicated (Fig. 16-6B).

Plain films of the lumbar or cervical spine are helpful when risk factors for vertebral fracture (trauma, chronic steroid use) are present. In the absence of risk factors, routine x-rays of the lumbar spine in the setting of acute, nonspecific, low back pain are expensive and rarely helpful. In general, the definition of soft tissue structures by MRI is superior, whereas CT-myelography provides optimal imaging of bony lesions in the region of the lateral recess and intervertebral foramen and is tolerated by claustrophobic patients.

Electromyography (EMG) can be used to assess the functional integrity of the peripheral nervous system (Chap. 357) in the setting of back pain. Sensory nerve conduction studies are normal when focal sensory loss is due to nerve root damage because the nerve roots are proximal to the nerve cell bodies in the dorsal root ganglia. The diagnostic yield of needle EMG is higher than that of nerve conduction studies for radiculopathy. Denervation changes in a myotomal (segmental) distribution are detected by sampling multiple muscles supplied by different nerve roots and nerves; the pattern of muscle involvement indicates the nerve root(s) responsible for the injury. Needle EMG provides objective information about motor nerve fiber injury when the clinical evaluation of weakness is limited by pain or poor effort. EMG and nerve conduction studies will be normal when only limb pain or sensory nerve root injury or irritation is present. Mixed nerve somatosensory evoked potentials and F-wave studies are of uncertain value in the evaluation of radiculopathy.