Understanding Somatosensation

• Somatosensation includes sensations from the integumentary and musculoskeletal systems.
• Somatosensation differs from specialized senses like sight and hearing.
• Somatosensory examination is important for understanding the competence/integrity of the nervous system.
• Somatosensory examination provides information about spinal tracts and brain function.
• It helps assess the extent of sensory loss, especially concerning nerve roots and peripheral nerves.

Why Somatosensation Matters

• It assists in diagnosis and provides prognostic information for patient management.
• It guides intervention and documents sensory recovery.
• Sensation plays key role in movement by guiding motor responses based on environment and context.
• Sensation adapts movements and shapes motor programs using feedback for corrections, feedforward and protection.

When to Conduct a Somatosensory Examination

• Clinical indications include risk factors, health/wellness needs, pathology/health conditions, impairments, and activity limitations.
• Findings can be found through history, systems review looking at such things as strength and reflexes, and dermatomal screens.

Sources and Effects of Sensory Dysfunction

• Sources of sensory dysfunction can include peripheral nerve damage, brain diseases, and spinal cord injuries.
• Examples of peripheral nerve damage include trauma, impingement, or compression.
• Metabolic issues like diabetes or thyroid problems, nutritional deficiencies (B12), and infections (Lyme disease, shingles, HIV) can be sources.
• Examples of sensory dysfunction include inability to balance while standing to put on pants and repeated injuries due to decreased sensation.
• Sensory dysfunction can cause difficulty gripping or manipulating objects for eating, dressing, and tool use.

Anatomy Review

• Relevant anatomical structures include the brain, spinal cord, nerve roots, peripheral nerves, and sensory receptors.

Sensory Receptor Types

• Mechano-receptors detect mechanical deformation.
• Thermo-receptors detect temperature.
• Noci-receptors detect pain.
• Chemo-receptors detect chemical substances.
• Photic receptors detect visible light.

Levels of Sensation

• Superficial sensation (exteroceptors) receive input from external sources and relates to pain, temperature, and light touch.
• Deep sensation (proprioceptors) receive input from muscles, tendons, ligaments, joints, and fascia, concerning position sense, movement, and vibration.

Combined Cortical Sensations

• These sensations require info from both superficial and deep.
• They include stereognosis, 2-point discrimination, barognosis, graphesthesia, tactile localization, texture, and double simultaneous stimulation.

Nerve Anatomy

• Spinal cord gives rise to nerve roots and spinal nerves then plexus and peripheral nerves.
• From there it goes onto sensory receptors.

Tracts

• Dorsal Column System carries conscious proprioception, vibration, and fine touch.
• Spinothalamic Tract carries pain, temperature, and crude touch.

Somatosensory Cortex

• Areas of high sensitivity have more sensory representation.
• It processes movement by determining initial position and detecting errors.

Sources of Dysfunction

• CNS (brain, nuclei, spinal cord, tracts) are impacted by stroke and spinal cord lesion.
• PNS (spinal nerves, peripheral nerves, sensory receptors) are impacted by compression and burns.

Nerve Injuries

• Types include myelopathy, nerve root avulsion, radiculopathy, plexopathy, and neuropathy.
• Neuropathy includes Mononeuropathy and Polyneuropathy
• Double Crush and Neural Tension can be included.

Peripheral Nerve Injuries

• Compression, blunt trauma, stretch, avulsion, severing, and disease can lead to peripheral nerve injuries.
• Wallerian degeneration is the degeneration of myelin and axons distal to the site of nerve injury.

Nerve Injury Classifications

• Neuropraxia involves a transient block with minimal structural damage.
• Axonotmesis involves axonal damage resulting in Wallerian degeneration with preserved neural tube architecture.
• Neurotmesis involves complete nerve destruction

Examination Prep

• Start with patient history and systems review.
• Formal somatosensory testing is included for tests and measures.
• Subjective information includes primary and medical history and neurological review of systems.
• Objective information includes light touch screens and diminished reflexes.

Somatosensory Test Selection

• Test selection depends on the goal: dermatome/peripheral nerve sensory distribution, superficial/deep sensors, a particular tract, or somatosensory cortex function.
• Examples of tests include touch awareness, pain perception, temperature, kinesthesia awareness, vibration perception, two-point discrimination, graphesthesia, texture recognition, and barognosis.

Therapist Preparation

• Therapists need equipment plus knowledge of anatomy and patterns.
• Reps to improve consistency in pressure and delivery.
• Tools, marking pencils, documentation, and something to block vision.

Tools for Touch Awareness

• Camel hair brush, cotton swab or ball, tissue, and monofilaments can be used.

Monofilaments

• Guidelines on pressure/monofilaments
• monofilament is perpendicular to skin, pressed until bent.
• Hold for 1-2 sec.

Norms & Values for Monofilaments

• 5.07 gauge/10 g indicates loss of protective sensation on the foot.

• ≤ 2.83 gauge/.07 g indicates normal sensation

Patient Preparation

• Give a full explanation of the test and purpose to a patient.
• Cognitively able, alert, oriented, plus appropriate age and ability.

Environment

• The environment should be quiet and free of distractions
• Patients should be positioning to relaxed and comfortable.

Orientation

• Properly demonstrate test procedures.
• Properly orient the patient with vision enabled.
• Get accurate responses

During the Exam

• Vision should be obstructed.
• An organized predictable routine is key.
• Cadence should be 2 seconds in between.
• A broad screen should be done and be aware of patient fatigue.
• Perform multiple trials for verification (x3).
• Sharp/Dull, Hot/Old, Soft fabric.
• Map exact boundaries and consider using a skin marker.

Additional Considerations

• Pain tests require similar processes and a sharp/dull variable.
• Localization tests require similar processes and adding instructions about where a sensation is felt.
• Double simultaneous stimulation involves two points at once rather than mapping exact boundaries.

What to look for

• When testing with dermatomes, peripheral nerve sensory distributions, etc.

Patterns

• Cross reference with myotomes, Motor nerve innervation, and sclerotomes.

Common Patterns of Sensory Loss

• CVA: Varied depending on location of brain infarct.
• MS: Unpredictable, Varied, and Scattered.
• Peripheral Neuropathy: Stocking and Glove and resulting from diabetes.
• Spinal Cord: Diffuse loss below the level of the injury.
• Spinal Nerve Root: Dermatome loss with Lots of overlap
• Peripheral Nerve: Cutaneous sensory distribution loss.

Reporting Results

• Document sensation types tested and tools used.
• Map the affected body surface.
• Report the outcome, scoring, and the patient's subjective responses.

Assessing

• Consider affected vs unaffected areas.
• Note speed/location and accuracy of map as well as fatigue.
• Look for patterns like Double Crush.