Diagnosing the exact cause of back pain can be difficult as back pain results from a variety of reasons - it could be muscular strain or have host of spinal causes like degenerative spine disease, wear and tear, anatomical defects, trauma, nerve compression, etc.
A spine specialist needs to piece together patient history, physical exam, imaging tests and neurological tests to confirm a diagnosis of spinal pain. Among these, assessment of neurological function is important in diagnosing and treating spinal issues. A neurological examination provides valuable insight to the specialist into the patient's brain, spinal cord, nerves and muscles.
After noting a detailed medical history of the patient, the specialist conducts a series of spine tests to inspect the spine, lower extremities and gait. Testing range of motion and manual muscle testing, along with palpation and some special testing is carried out to confirm findings.
- Nerve root stretching
- Motor examination
- Sensory examination
- Deep tendon reflexes
Nerve root stretching
Disturbance to nerve roots due to lesions or herniated discs causes pain if nerve roots are stretched. This forms the basis of a neurological test called the straight-leg raising (SLR).
Motor examination
The doctor asks the patient to perform certain voluntary movements to assess the condition of a nerve by checking the strength of a given body part supplied by it. For example, proximal leg weakness is determined by asking the patient to attempt to rise from a squatting position. Gastrocnemius weakness is detected through repeated rising up on the toes.
Sensory examination
Nerves originating from the spinal cord divide into motor and sensory nerves. It is the sensory nerves that give sensation to the skin. In this test, the doctor applies pinprick and touch sensation to specific areas on the skin that are supplied by specific spinal nerves. Any loss of sensation indicates and localizes nerve root involvement.
However, due to the wide overlap of root distributions, lesion of a single root may only produce a mild reduction in sensitivity of the area it supplies. The major sensations that a doctor looks out for are numbness, tingling, burning and pain in the back or extremities, which sometimes radiate outwards. An example of such pain is sciatica that radiates into the leg.
The specialist doctor may use a swab, cotton, pin or paperclip to test if the feeling in arms and legs is symmetrical or not. Abnormal responses may hint towards a nerve root problem.
Deep tendon reflexes
A reflex is an involuntary muscular response to tapping on of a nerve. A rubber hammer is tapped on a tendon and the reflex generated by the patient is recorded. Absence of any form of reflex response could be an indicator of damage to the spinal cord, nerve root, peripheral nerve or muscle. The abnormal response could be due to disruption of sensory (feeling) nerves, motor (movement) nerves, or both.
Deep tendon reflexes are evaluated for wrist extensors, biceps, triceps and finger flexors in the upper extremities. The anal wink and bulbocavernosus reflexes, which affect the bowel and bladder function, are also assessed (their presence indicates emergence from spinal shock).
Some of the tests conducted during a neurological exam are as follows:
Straight-leg raising (SLR)
This can be performed by the patient, either sitting or lying down. The extended leg is raised to check if the motion elicits pain in the leg, buttock or back, and if it does, then at what angle from the horizontal plane does it occur.
Lasegue test
This test is performed in the same fashion as the straight-leg raise test in lying form, and is used to evaluate lumbar nerve impingement or irritation. It is different from SLR in that once the patient complains of pain at a particular angle of the raised leg, the leg is slowly lowered 5-10 per cent or until the radicular symptoms disappear, and the doctor dorsiflexes the foot in this lowered position. A positive test will reproduce the same symptoms in this modified position.
Slump test
Used to evaluate lumbar root impingement or irritation, this test starts with the patient seated on a table with both hips and knees at right angles. The patient is instructed to slump forward while keeping the head and neck in neutral position. Physician extends one leg with one hand while applying pressure on the patient's thoracic spine. The patient is then instructed to lower chin to the chest, producing a cervical flexion. A positive Slump test reproduces the radicular symptoms. The test is repeated with the other side.
Femoral nerve traction test
This test evaluates the pathology of the femoral nerve and the nerve roots coming out of the third and fourth lumbar spinal segments. The patient lies on the unaffected side with the unaffected limb slightly flexed at the hip and knee. Neck is slightly flexed, and back is in a non-hyperextended position. The examiner extends the patient's hip while standing behind the patient, flexes the knee and puts tension on the femoral nerve. Positive test result is reproduction of radicular symptoms down the front of the thigh.
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