Makindo Medical Notes

Related Subjects: |Neurological History taking |Cortical functions |Motor System |Sensory System |Mental State Examination |Speech and Language Exam |Cranial nerves and examination |Assessing Cognition

Anatomy

• Conscious sensation travels from the sense organ to the contralateral parietal lobe.
• From the sensory receptor, it enters the spinal cord through the dorsal root.
• Travels through two main pathways:
  • Dorsal Columns:
    • Carry afferent signals related to proprioception, vibration, and fine touch.
    • Fibers remain on the same side of the spinal cord before crossing at the foramen magnum.
  • Spinothalamic Tracts:
    • Fibers cross over almost immediately after entering the spinal cord.
    • Ascend in the spinal cord to the ipsilateral thalamus and then cross over to the contralateral parietal lobe.
• Basic sensory examination:
  • Assess cutaneous sensation with pinprick and light touch (cotton wool) over dermatomes, comparing both sides.
  • Test for temperature and proprioception.

Sensory Modalities

• Proprioception (Dorsal Column):
  • Testing proprioception involves moving the distal joints, such as the toes or fingers, and asking the patient to describe the direction (up/down) with eyes closed.
  • Romberg Test: The patient stands with feet together. Loss of balance with eyes closed suggests a problem with proprioception and dorsal column function.
• Vibration (Dorsal Column):
  • Use a 128 Hz tuning fork on bony prominences (e.g., big toe, medial malleolus). Check if the patient can distinguish between vibration and no vibration.
• Temperature (Spinothalamic):
  • Test by using a cold object (e.g., tuning fork). Abnormal temperature perception can indicate spinothalamic tract lesions, like hemi-cord or lateral medullary syndromes.
• Fine Touch (Dorsal Column):
  • Use cotton wool to test different dermatomal areas. Move from areas with sensory loss to normal sensation.
• Pinprick (Spinothalamic):
  • Use a disposable pin to test pain perception. Test from areas of sensory loss toward normal areas.

Interpretation

• Patterns of sensory loss:
  • Sensory loss over one side of the body (face, arm, and leg) suggests contralateral intracranial pathology.
  • Cape-like loss of pain and temperature over the shoulders and arms suggests syringomyelia.
  • Loss of proprioception could indicate B12 deficiency (Subacute Combined Degeneration or Tabes Dorsalis).
  • Glove and stocking distribution suggests peripheral neuropathy.
  • Sensory loss below a certain level suggests spinal cord disease.
  • Reduced perineal sensation suggests cauda equina damage.
• Perineal Examination:
  • Important in suspected cauda equina syndrome. Ask about incontinence and perform a rectal examination to assess anal tone.

Dermatomes

• Thumb: C6
• Middle finger: C7
• Little finger: C8
• Breast nipple: T4
• Umbilicus: T10
• Big toe: L5
• Little toe: S1
• Inner thigh: S2
• Saddle area: S3-S5

Examination Steps

1. Introduction and Consent

• Introduce Yourself: Clearly state your name and role.
• Explain the Procedure: Briefly describe the sensory examination to the patient.
• Obtain Consent: Ensure the patient consents to the examination.

2. General Principles

• Positioning: The patient should be seated or lying down comfortably.
• Exposure: Expose only the areas being tested while maintaining patient privacy.
• Equipment: Ensure availability of cotton wool, a pin, tuning fork, and temperature probes.

3. Light Touch Assessment

• Equipment: Use cotton wool.
• Procedure: Ask the patient to close their eyes and gently touch different parts of the body.
• Instructions: The patient should say "yes" or "now" when they feel the touch.
• Interpretation: Compare symmetry between both sides of the body.

4. Pain (Sharp/Dull) Assessment

• Equipment: Use a neurotip or a safety pin with sharp and blunt ends.
• Procedure: Ask the patient to close their eyes and alternate between sharp and blunt touch.
• Instructions: The patient should identify "sharp" or "dull".
• Interpretation: Inability to distinguish may indicate nerve damage.

5. Temperature Assessment

• Equipment: Use two test tubes or temperature probes.
• Procedure: Ask the patient to close their eyes and distinguish between warm and cold objects on the skin.
• Interpretation: Abnormal results suggest a spinothalamic tract lesion.

6. Vibration Assessment

• Equipment: A 128 Hz tuning fork.
• Procedure: Strike the fork and place it on a bony prominence.
• Instructions: The patient reports when they feel the vibration and when it stops.
• Interpretation: Diminished vibration sense may indicate peripheral neuropathy.

7. Proprioception (Joint Position Sense)

• Procedure: Hold the patient’s finger or toe by the sides, move it up or down, and ask them to identify the direction with eyes closed.
• Interpretation: Inability to identify movement suggests dorsal column dysfunction.

8. Discriminative Sensation Assessment

• Two-Point Discrimination: Test with calipers or a paperclip to determine the minimum distance at which two points are distinguishable.
• Graphesthesia: Draw a number or letter on the patient’s palm and ask them to identify it.
• Stereognosis: Place an object in the patient’s hand and ask them to identify