Medicine

Basics of an Orthopedic Neurological Exam

 

Neurological Exam

Indications:

  • Symptoms
    • Weakness
    • Incordination
    • change in sensibility
  • Signs
    • Disorder of Neck or Back

Overview

  • Inspect
    • General Appearance
  • Motor
    • tone, power, reflexes
  • Sensory
    • superficial (skin) and deep sensibility

Appearance

Some appearances are pathognomonic eg

  • Claw hand - Ulnar nerve lesion
  • Wrist Drop - Radial Nerve palsy
  • Waiters Tip - brachial plexus injury

waiters tip

Some are seen only on movement

  • Dangling arm - brachial plexus injury
  • flail lower limb - poliomyelitis
  • symmetrical paralysis - spinal cord lesion
  • foot drop gait (toes drag on ground) - sciatic/peroneal nerve damage
  • Jerky spastic movements - cerebral palsy

Look for trophic changes (signify loss of sensibility)

  • Smooth hairless skin that looks stretched
  • atrophy of the fingertips and nails
  • scars of accidental burns
  • ulcers that refuse to heal

Muscle wasting if localized indicates nerve damage

Tone

Tone in divided muscle groups is tested by moving the nearby joint to stretch the muscle. Increased tone (spasticity) is characteristic of upper motor neuron lesions (cerebral palsy, stroke etc). don’t confuse with rigidity (lead pipe or cog wheel effect) which is seen in parkinsonism.
Decreased tone is seen in lower motor neuron diseases (poliomyelitis).
Power is decreased in rigidity, spasitcity and flaccidity.

Power

Motor function is tested by having the patient perform movements normally activated by specific nerves.
The simplest way to test for power is to tell the patient to keep limb in “test position” & resist any change by the examiner. Examine normal limb first. Finer muscle movement is best assessed by doing the action yourself and asking the patient to repeat.

Use MRC Scale

mrc scale

Tendon reflexes

Caused by rapidly stretching a tendon near insertion. usually done with patella hammer and with too much force. Better to start with a series of taps with the most forceful first and reduce force until there is no response. Helps to differentiate between diminshed and absent.

  • Upper limbs
    • Biceps
    • Triceps
    • Brachioradialis
  • Lower Limb
    • Patella
    • Achilles

There are monosynaptic segmental reflexes (shortcut through the spinal cord at a segmental level) therefore diminished or absent reflexes show pathology in the posterior nerve root, anterior horn cell, motor nerve root or peripheral nerve. This is reliable enough to find the segmental level of dysfunction (C5- C6 for abnormality in biceps reflex, S1 for abnormality in ankle reflex). Brisk reflexes are characteristic of upper motor neuron lesions (cerebral palsy, stroke, injury to spinal cord). This is because there is release from the normal central inhibition, therefore exaggerated response to tendon stimulation. May manifest as ankle clonus (sharp upward jerk on the foot aka dorsiflexion, would induce repetitive clonic movements) & a sharp downward push on the patella may elicit patella clonus.

Plantar Reflex

Forceful stroking of the sole produces flexion of the toes (or no response at all). An extension response (big toe extends while others flex) is characteristic of upper motor neuron lesions. This is a positive Babinski’s Sign.
It is normally seen in young infants but represents cerebral immaturity and normally disappears at 18 months.

Sensibility

Sensibility to touch and pin prick may be increased (hyperaesthesia) or unpleasant (dysaesthesia) in certain irritative nerve lesions. More often it is diminished (hypoaesthesia) or absent (anesthesia) signifying pressure or interruption of peripheral nerves, in the nerve root or sensory pathways of the spinal cord.
It can be mapped out dermatomes.
Brisk percussion along the course of an injured nerve may elicit a tingling sensation distally (Tinel’s Sign). Where there is hypersensitvity marks the site of abnormal nerve sprouting & if it migrates distally, it signifies nerve regeneration. If unchanged, it suggests local neuroma. Temperature & two point discrimination is also used.

Deep sensibility can be examined by the vibration test, position sense, stereognosis and balance

For vibration, a tuning fork is placed over a bony prominence & the patient is asked to say when they feel the vibrations disappear (with eyes closed of course). Compare bilaterally.

Position sense can be tested by asking the patient to find parts of their body with their finger tip (eg. tip to nose etc.) with their eyes closed. Joint position is done by grasping the big toe & with the patients eyes closed, say whether their toe is up or down. The examiner changes its orientation randomly and the test is repeated.

Stereognosis is the ability to recognize shapes & texture by feel alone. Eyes are closed and they are asked to identify objects placed in their hand.

Deep sensation runs up the posterior columns therefore causes of reduced deep sensations can result from pathology in

  • the peripheral nerves
  • spinal cord lesions that include the posterior columns
    • eg Tabes Dorsalis (syphilitic myelopathy, a slow degeneration of the dorsal neuronal tracts, ie demyelination, affects parts closest to the back.)

Balance is also carried here and asking the patient to stand with eyes closed is the Rombergs test. Positive s there is excessive body swing.

Cortical & Cerebellar Function

Staggering knee may imply unstable knee or a disorder of the spinal cord or cerebellum. Do both muscular skeletal and CNS exam in full.