CALDERON, GARCIA, HARDIN, MANABAT, SOLIS 1 of 4

SENSORY EXAMINATION

2.3-D August 11, 2014

PLM CM Dr. Guzman

Legend: normal text lecture/old trans; Bates italics; transers notes red text.

INTRODUCTION

Steps in the Diagnosis of Neurologic Diseases: 1. Mental Status Exam 2. Gait and Station 3. Cranial Nerves

4. Motor System 5. Coordination 6. Reflexes 7. Sensation 8. Head and Neck 9. Spine and Skin

IMPORTANCE: By identifying the distribution of sensory abnormalities and the kinds of sensations affected, you can infer where the causative lesion might be.

SENSORY PATHWAY

Sensory input travels up through the spinal cord along specific paths, with the precise route defined by the type of sensation being transmitted.

Ultimately, the sensory nerves terminate in the brain, where the impulses are integrated and perception occurs.

To evaluate the sensory system, you will test several kinds of sensation:

o Pain and temperature (spinothalamic tracts) o Position and vibration (posterior columns) o Light touch (both of these pathways) o Discriminative sensations, which depend on some

of the above sensations but also involve the cortex

Face

Sensory testing of the face is discussed in the Cranial Nerves

Extremities

Testing of the extremities focuses on the two main afferent pathways: o Spinothalamics:

- These nerves detect pain, temperature and crude touch.

- Pathway: peripheral impulses enter spinal cord cross to the other side within one or two vertebral levels of entry point continue up that side to the brain terminate in the cerebral hemisphere on the opposite side of the body from where they began.

o Dorsal Columns: - These nerves detect position (a.k.a.

proprioception), vibratory sensation and light touch.

- Pathway: peripheral impulses enter spinal cord move up to the base of the brain on the same side of the cord as where they started upon reaching the brain stem they cross to the opposite side terminate in the cerebral hemisphere on the opposite side of the body from where they began.

lesion of the sensory cortex

may not impair the perception of pain, touch, and position but does impair finer discrimination

disease of the posterior columns

Loss of position and vibration sense with preservation of other sensations

transection of the spinal cord

Loss of all sensations from the waist down, together with paralysis and hyperactive reflexes in the legs

Crude and light touch are often preserved despite partial damage to the cord, because impulses originating on one side of the body travel up both sides of the cord.

Dermatomes

Dermatome: a band of skin innervated by the sensory root of a single spinal nerve.

Knowledge of dermatomes helps you localize neurologic lesions to a specific level of the spinal cord, particularly in spinal cord injury.

In spinal cord injury, the sensory level may be several segments lower than the spinal lesion, for reasons that are not well understood. Tapping for the level of vertebral pain may be helpful.

Dermatome levels are more variable than the diagrams suggest (see page 4). They overlap at their upper and lower margins and also slightly across the midline.

SENSORY FUNCTION EXAMINATION

GENERAL INSTRUCTIONS AND PATTERNS OF TESTING

(not in particular order) 1. Sensory testing quickly fatigues many patients, producing

unreliable results conduct the examination as efficiently as possible

2. Pay special attention to areas o where there are symptoms (e.g. numbness or pain) o where there are motor or reflex abnormalities that

suggest a lesion of the spinal cord or peripheral nervous system

o where there are trophic changes (e.g. absent/ excessive sweating, atrophic skin, or cutaneous ulceration

3. Repeat testing at another time is often required to confirm abnormalities.

4. Compare symmetrical areas on the two sides of the body. o A Hemisensory loss pattern suggests a lesion in

the opposite cerebral hemisphere o A Sensory level loss pattern suggests a spinal

cord lesion 5. Compare distal and proximal areas of the extremities.

o Further, scatter the stimuli so as to sample most of the dermatomes and major peripheral nerves.

o One suggested pattern of testing: 1. both shoulders (C4) 2. inner and outer aspects of forearms (C6&T1) 3. thumbs and little fingers (C6 and C8) 4. fronts of both thighs (L2) 5. medial and lateral calves (L4 and L5) 6. little toes (S1) medial buttock (S3)

o Symmetric distal sensory loss suggests a polyneuropathy. You may miss this finding unless you compare distal and proximal sensation.

o When testing vibration and position sensation, first test the fingers and toes. If these are normal, you may safely assume that more proximal areas will also be normal.

6. Vary the pace of your testing so that the patient does not merely respond to your repetitive rhythm.

7. When you detect an area of sensory loss or hypersensitivity, map out its boundaries in detail.

o Stimulate first at a point of reduced sensation, and move by progressive steps until the patient detects the change.

8. When you detect abnormal findings, correlate them with motor and reflex activity. Assess the patient carefully as you consider the following questions:

o Is the underlying lesion central or peripheral? Is the sensory loss bilateral or unilateral?

o Does it have a pattern suggesting a dermatomal distribution, a polyneuropathy, or a spinal cord syndrome with a loss of pain and temperature sensation but intact touch and vibration?

9. Explain each test before you do it. 10. Unless otherwise specified, the patients eyes should

be closed during the actual testing.

PRIMARY MODALITY TESTING

(See pages 3-4)

CALDERON, GARCIA, HARDIN, MANABAT, SOLIS 2 of 4

SENSORY EXAMINATION

2.3-D August 11, 2014

PLM CM Dr. Guzman

SPECIAL TESTING FOR EARLY DIABETIC NEUROPATHY

A careful foot examination should be performed on all patients with symptoms suggestive of sensory neuropathy or at particular risk for this disorder (e.g. anyone with diabetes).

Monofilament Testing

Disposable monofilaments are small nylon fibers designed such that the normal patient should be able to feel the ends when they are gently pressed against the soles of their feet.

Have the patient close their eyes.

Touch the monofilament to 5-7 areas on the bottom of the patient's foot. Pick locations so that all of the major areas of the sole are assessed. Avoid calluses, which are relatively

insensate

Normal Result (left pic): Patient is able to detect the filament when the tip is lightly applied to the skin Impaired sensation (right pic): If the force required to provoke a sensory response is strong enough to bend the monofilament

Neuropathic Ulcer

A large ulcer has developed in this patient with severe diabetic neuropathy.

SELECTED SENSORY PROBLEMS

Diffuse Distal Sensory Loss

A number of chronic systemic diseases affect nerve function; most commonly occurring is diabetes.

This first affects the most distal aspects of the nerves and then moves proximally. Thus, the feet are the first area to be affected.

As it is a systemic disease, it occurs simultaneously in both limbs.

Example: In the picture, all sensation in the hand is lost. Repetitive testing reveals a gradual change to normal sensation at the wrist. This fits neither a peripheral nerve nor a dermatomal distribution. If bilateral, this pattern of loss is referred to as a Stocking (if feet) or

Glove (if hands) Distribution Impairment, as the area involved covers an entire distal region, much as a sock or glove would cover a foot or hand. Such deficits may be associated with neuropathic pain, a continuous burning sensation affecting the distal extremity.

Glove and stocking sensory loss of a polyneuropathy is often seen in alcoholism and diabetes.

This is more common in the feet than in the hands. The more advanced the disease, the higher up the leg this will occur.

Hands are less commonly affected than feet as the nerves traveling to the legs are longer and thus at much greater risk.

Peripheral Nerve Palsy

A specific peripheral nerve can become dysfunctional, for example, as the result of trauma or infarction (another complication of diabetes).

There will be a pattern of sensory impairment that follows the distribution of the nerve.

Radial nerve palsy o May occur if an intoxicated person falls asleep in a

position that puts pressure on the nerve as it travels around the humerus

o Intoxication-induced loss of consciousness then prevents the patient from reflexively changing position (normally, this is how we prevent nerves from being exposed to constant direct pressure).

o The resultant sensory loss would involve the back of the hand and forearm. Motor function would also be affected.

Testing of the sacral nerve roots, serving the anus and rectum, is important if patients complain of incontinence, inability to defecate/urinate, or there is otherwise reason to suspect that these roots may be compromised (e.g. in cauda equine syndrome).

Cauda Equina syndrome o Multiple sacral and lumbar roots become compressed

bilaterally (e.g. by posteriorly herniated disc material or a tumor).

o Patient is unable to urinate, as the lower motor neurons carried in these sacral nerve roots no longer function - No way to send impulse to the bladder instructing

it to contract - No way to be aware that bladders are full - Loss of anal sphincter tone, as appreciated on

rectal exam - Ability to detect pin pricks in the perineal area

(a.k.a. saddle distribution) also diminished

CALDERON, GARCIA, HARDIN, MANABAT, SOLIS 3 of 4

SENSORY EXAMINATION

2.3-D August 11, 2014

PLM CM Dr. Guzman

PRIMARY MODALITY TESTING

Primary modality to be tested

Procedure Remarks

LIGHT TOUCH (using cotton wisp)

1. Touch skin lightly, avoiding pressure 2. Ask the patient to respond whenever a touch is felt

and compare one area with another

Anesthesia: absence of touch sensation

Hypesthesia: decreased sensitivity

Hyperesthesia: increased sensitivity

Calloused skin is normally relatively insensitive and should be avoided.

DO NOT TEST IF THERE IS ALREADY NUMBNESS OR NEUROPATHY!

VIBRATION (using 128 Hz tuning fork: relatively low-

pitched)

1. Test with a non-vibrating tuning fork first to ensure that the patient is responding to the correct stimulus.

2. Tap tuning fork on the heel of your hand 3. Place the stem of the fork over the distal

interphalangeal joint of the patient's index fingers and big toes.

4. Ask what the patient feels 5. If you are uncertain whether it is pressure or

vibration, ask the patient to tell you when the vibration stops, and then touch the fork to stop it.

6. If vibration sense is impaired, proceed to more proximal bony prominences (e.g. wrist, elbow, medial malleolus, patella, anterior superior iliac spine, spinous processes, and clavicles)

Vibration sense is often the first sensation to be lost in a peripheral neuropathy. Common causes include diabetes and alcoholism.

Vibration sense is also lost in posterior column disease (e.g. tertiary syphilis or vitamin B12 deficiency)

Testing vibration sense in the trunk may be useful in estimating the level of a cord lesion.

POSITION SENSE (PROPRIOCEPTION)

1. Grasp the patient's big toe, hold it by its sides between your thumb and index finger.

2. Pull it away from the other toes to prevent extraneous tactile stimuli from affecting testing.

3. Demonstrate "up" and "down as you move the patients toe clearly upward and downward.

4. With the patient's eyes closed, ask the patient to identify the direction as you move the toe.

5. If position sense is impaired move proximally to test the ankle joint.

6. Test the fingers in a similar fashion. If indicated move proximally to the metacarpophalangeal joints, wrists, and elbows.

Greater deficits are characterized by having to move a more proximal joint such as ankle, knee or hip for the patient to appreciate the movement.

Loss of position sense, like loss of vibration sense: o tabes dorsalis o multiple sclerosis o B12 deficiency from posterior

column disease o peripheral neuropathy from

diabetes

PAIN (using sterile, sharp pin, broken cotton

swab)

1. Touch the patient with the sharp or dull end and ask them to identify sharp or dull.

2. One can also ascend from the foot upwards and ask the patient to identify the level where appreciation of sharpness occurs or where an appreciable increase in sensation occurs.

Analgesia: absence of pain sensation

Hypalgesia: decreased sensitivity to pain

Hyperalgesia: increased sensitivity to pain

To prevent transmitting a blood-borne infection, discard the pin or other device safely. Do not reuse it on another person.

TEMPERATURE (Using a cold tuning fork or hot and cold water in a test tube)

Ask them to identify when touched with hot or cold.

Often omitted if pain sensation is normal

Levels and laterality can also be tested as described for pain and light touch..

DISCRIMINATION (Since these tests are dependent on touch and position sense,

they cannot be performed when the

tests above are clearly abnormal)

Graphesthesia (Number Identification) 1. With the blunt end of a pen or pencil, draw a

large number in the patient's palm. 2. Ask the patient to identify the number.

Stereognosis (Use as an alternative to

graphesthesia): The ability to recognize an object by feeling it.

1. Place a familiar object in the patient's hand (coin, paper clip, pencil, etc.).

2. Ask the patient to tell you what it is.

Two-Point Discrimination 1. Use an opened paper clip to touch the patient's

finger pads in two places simultaneously. 2. Alternate irregularly with one-point touch. 3. Ask the patient to identify "one" or "two." 4. Find the minimal distance at which the patient

can discriminate (normally less than 5 mm on the finger pads)

Tested when motor impairment, arthritis, or other conditions prevent the patient from manipulating an object well enough to identify it

The inability to recognize numbers suggests a lesion in the sensory cortex

Normally a patient will manipulate it skillfully and identify it correctly within 5 seconds.

Asking the patient to distinguish heads from tails on a coin is a sensitive test for stereognosis

Astereognosis: inability to recognize objects placed in the hand

These stimuli are carried via the Dorsal Columns.

It is a useful test if a discrete peripheral neuropathy is suspected (e.g. injury to the radial nerve).

CALDERON, GARCIA, HARDIN, MANABAT, SOLIS 4 of 4

SENSORY EXAMINATION

2.3-D August 11, 2014

PLM CM Dr. Guzman

Extinction 1. Touch the same spot on both sides of the body

at the same time (e.g. the left and right forearms.)

2. Ask the individual to describe how many spots are being touched.

Point Localization 1. Touch the surface of the skin and remove the

stimulus quickly while patients eyes are closed.

2. Ask to open his/her eyes and ask to touch the spot where the sensation was felt.

Normal: both sides are felt

(+) sensory lesions: the individual will sense only one. The stimulus on the side opposite the damaged cortex is extinguished.

This test, together with extinction, is especially useful on the trunk and the legs.

Lesions of the sensory cortex impair the ability to localize points accurately

Common peripheral nerves, territories of innervation, and clinical correlates.

Peripheral Nerve

Sensory Innervation

Motor Innervation Contributing Spinal Nerve

Roots

Clinical Correlate

Radial Nerve Back of thumb, index, middle, and ring finger; back of

forearm

Wrist extension and abduction of thumb

in palmer plane

C6, 7, 8 At risk for compression at humerus, known as "Saturday Night Palsy

Ulnar Nerve Palmar and dorsal aspects of pinky and

of ring finger

Abduction of fingers (intrinsic muscles of

hand)

C7, 8 and T1 At risk for injury with elbow fracture. Can get transient symptoms when inside of elbow is struck ("funny

bone" distribution)

Median Nerve Palmar aspect of the thumb, index, middle

and ring finger; palm below these

fingers.

Abduction of thumb perpendicular to

palm (thenar muscles).

C8, T1 Compression at carpal tunnel causes carpal tunnel syndrome

Lateral

Cutaneous Nerve of Thigh

.Lateral aspect thigh L1, 2 Can become compressed in obese patients, causing numbness over its

distribution

Peroneal Nerve

Lateral leg, top of foot

Dorsiflexion of foot (tibialis anterior

muscle)

L4, 5; S1 Can be injured with proximal fibula fracture, leading to foot drop

(inability to dorsiflex foot)

^FIGURE: Peripheral Nerve and Dermatomal Distributions on anterior surface (left) and posterior surface (right)