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Do the sensory system examination in the given subject mbbs 1st year practical

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I now have comprehensive information from the textbooks. Let me compile the full sensory system examination write-up for MBBS 1st year practical.

Sensory System Examination - MBBS 1st Year Practical

INTRODUCTION

The sensory system examination assesses the integrity of sensory pathways from peripheral receptors through the spinal cord to the cerebral cortex. It is divided into:
  1. Superficial (Exteroceptive) Sensations - Touch, Pain, Temperature
  2. Deep (Proprioceptive) Sensations - Vibration, Position sense, Deep pressure pain
  3. Cortical (Discriminative) Sensations - Two-point discrimination, Graphesthesia, Stereognosis, Tactile localization

GENERAL RULES BEFORE STARTING

  • Always ask the subject about any sensory complaints before testing.
  • The subject's eyes must be closed throughout the examination.
  • First familiarize the subject with each stimulus on a normal area before formal testing.
  • Proceed from an area of reduced sensation toward normal to map boundaries accurately.
  • Do not suggest or lead the subject - simply ask them to say "yes" each time a sensation is felt.
  • Do not test when the subject is fatigued or inattentive.
  • Compare symmetrical areas on both sides of the body.
  • Record findings systematically (narrative or shading on a body diagram).

A. SUPERFICIAL (EXTEROCEPTIVE) SENSATIONS

1. Light Touch (Tactile Sensation)

Apparatus: Wisp of cotton wool
Procedure:
  1. Ask the subject to close their eyes.
  2. Touch a wisp of cotton lightly to the skin of a normal area first - tell the subject this is what they should feel.
  3. Then touch various areas of the skin lightly with the cotton wool.
  4. Ask the subject to say "yes" every time they feel the touch.
  5. Compare symmetrical areas on both limbs and trunk.
  6. If an area of reduced sensation is found, map its boundaries - proceed from numb to normal.
Normal Response: Subject correctly identifies all touch stimuli bilaterally.
Note: Cornified areas (palms, soles) need a slightly firmer stimulus. Hair-bearing skin is more sensitive due to nerve endings around follicles.

2. Pain (Pin-Prick Sensation)

Apparatus: A clean, sterile pin (disposable)
Procedure:
  1. Show the subject the pin and explain the difference between the "sharp" tip and "dull" end.
  2. Ask the subject to close their eyes.
  3. Apply the pin alternately with the blunt and sharp ends on a normal area first to ensure the subject understands.
  4. Then apply the pin to various parts of the body, alternating sharp and blunt, and ask "sharp or dull?"
  5. Apply stimuli approximately one per second; do not repeat over the same spot (avoids temporal summation).
  6. Compare symmetrical areas systematically.
  7. Map any area of hypoalgesia or analgesia from reduced to normal.
Normal Response: Subject correctly identifies sharp vs. dull in all areas tested.
Note: Ask the subject to rate pin sensation on a scale of 1-10 in different areas; a report of 8-9 vs. 10 is usually insignificant. Avoid a pinwheel (Wartenberg wheel) due to infection risk.

3. Temperature Sensation

Apparatus: Two test tubes - one with cold water (20°C/68°F) and one with warm water (45°C/113°F). Alternatively, the two sides of a 128 Hz tuning fork (one side warmed by rubbing).
Procedure:
  1. Ask the subject to close their eyes.
  2. Apply each tube alternately to the skin in random order.
  3. Ask the subject to say "hot" or "cold" each time.
  4. Compare symmetrical areas on both sides of the body.
  5. Map any area of impaired thermal sensation.
Normal Response: Subject correctly differentiates hot and cold on all areas tested.
Note: Normal subjects can detect a temperature difference of as little as 1°C in the range of 28-32°C. If temperature is below 10°C or above 50°C, thermal sensation blends with pain. Temperature and pain share the same pathway (spinothalamic tract), so impairment often appears together.

B. DEEP (PROPRIOCEPTIVE) SENSATIONS

4. Vibration Sense (Pallesthesia)

Apparatus: 128 Hz tuning fork
Procedure:
  1. Strike the tuning fork to set it vibrating.
  2. Place the base firmly over a bony prominence (e.g., dorsum of distal interphalangeal joint of the big toe or finger, medial malleolus, patella, anterior tibial spine).
  3. Ask the subject to tell you when they first feel the vibration and when it stops.
  4. Note the duration the subject perceives vibration.
  5. When the subject reports they no longer feel it, quickly transfer the fork to your own corresponding body part and note if you still feel it (or compare with a normal limb).
  6. Compare symmetrical areas; test distal before proximal.
Normal Response: Subject perceives vibration over all bony prominences tested.
Grading: If vibration disappears at the ankle but is felt at the knee, this suggests a peripheral neuropathy (length-dependent pattern).

5. Joint Position Sense (Proprioception / Kinesthesia)

Apparatus: None (examiner's hands)
Procedure:
  1. Ask the subject to close their eyes.
  2. Grasp the digit (great toe or finger) at the sides (not top and bottom - this avoids pressure cues).
  3. First demonstrate a clearly "up" and "down" movement with the eyes open.
  4. Then, with eyes closed, move the digit slightly up or down and ask the subject to say "up" or "down."
  5. Use very small movements once the subject understands.
  6. Repeat several times to exclude guessing.
  7. If impaired distally, test the next proximal joint (ankle, then knee, etc.).
Normal Response: Subject correctly identifies the direction of very slight joint movements (as small as 1-2 degrees of arc).

6. Romberg's Test (Tests Proprioception + Visual Integration)

Procedure:
  1. Ask the subject to stand with feet together.
  2. Observe for swaying with eyes open first.
  3. Then ask the subject to close their eyes and observe for swaying or loss of balance.
Normal Response: Minimal or no swaying with eyes closed.
Positive Romberg's Sign: Marked increase in swaying or tendency to fall with eyes closed but not with eyes open - indicates impaired proprioception (posterior column lesion). Note: Cerebellar ataxia causes unsteadiness with both eyes open AND closed.

7. Deep Pressure Pain

Procedure:
  1. Apply firm pressure with your thumb or finger on tendons (Achilles tendon), muscles (calf muscles), or bony prominences.
  2. Ask whether the subject feels discomfort or pain.
Normal Response: Deep pressure causes some discomfort.
Clinical Note: In tabes dorsalis (neurosyphilis), deep pressure pain is lost. This test is omitted in routine examinations.

C. CORTICAL (DISCRIMINATIVE) SENSATIONS

(These tests require that primary sensation is intact first)

8. Two-Point Discrimination

Apparatus: Dividers (compass) with blunt tips, or a paper clip bent to different widths.
Procedure:
  1. Ask the subject to close their eyes.
  2. Apply both points simultaneously (not one after another) to the skin.
  3. Start with a distance wider than the normal threshold for that area.
  4. Gradually decrease the distance until the subject can no longer distinguish two points from one.
  5. Record the minimum distance at which two points can be discriminated.
Normal Values:
Body PartMinimum Discriminable Distance
Fingertip3-5 mm
Palm8-15 mm
Dorsum of hand/foot20-30 mm
Trunk4-7 cm
Lip2-3 mm
Tongue tip1 mm
Clinical Significance: Impaired in parietal lobe lesions.

9. Graphesthesia (Figure Writing)

Apparatus: Blunt object (e.g., pencil cap, pen tip)
Procedure:
  1. Ask the subject to close their eyes.
  2. Write a number or letter on the subject's palm (should be >4 cm on the palm, or smaller on the fingertip).
  3. Ask the subject to identify the number or letter written.
  4. Test both palms.
Normal Response: Subject correctly identifies numbers/letters traced on the skin.
Clinical Significance: Impaired in parietal lobe lesions (posterior cortex damage).

10. Stereognosis

Apparatus: Common objects - coin, key, button, pen
Procedure:
  1. Ask the subject to close their eyes.
  2. Place an object in the subject's hand and allow them to feel it (do not let them see it).
  3. Ask them to identify the object.
  4. Test both hands separately.
Normal Response: Subject correctly identifies familiar objects by touch alone.
If impaired = Astereognosis: Indicates a contralateral parietal lobe lesion.

11. Tactile Localization

Procedure:
  1. Touch the subject's skin at a point while eyes are closed.
  2. Ask the subject to point to (or touch) the exact spot stimulated with their fingertip.
Normal Response: Accurate localization within a small margin.

SUMMARY TABLE

SensationApparatusPathway
Light TouchCotton woolDorsal column + Spinothalamic
PainPinSpinothalamic tract
TemperatureTest tubes (hot/cold)Spinothalamic tract
Vibration128 Hz tuning forkDorsal column - Medial lemniscus
Joint PositionExaminer's handsDorsal column - Medial lemniscus
Two-point discriminationCompass/dividersParietal cortex
GraphesthesiaBlunt penParietal cortex
StereognosisObjectsParietal cortex

RECORDING OF FINDINGS

After completing the examination, record:
  • Normal / Impaired for each modality
  • Laterality (right, left, bilateral)
  • Distribution (dermatomal, peripheral nerve, stocking-glove, hemibody)
  • Level (if there is a sensory level, mark it on the trunk)
Example report: "Light touch, pain, and temperature intact bilaterally. Vibration and joint position sense reduced in both lower limbs distally (below the knees). Two-point discrimination, graphesthesia, and stereognosis normal."
Sources: Adams and Victor's Principles of Neurology, 12th Ed. (pp. 174-177); Neuroanatomy through Clinical Cases, 3rd Ed.
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