Understanding Somatosensation

• Somatosensation is sensation received from the integumentary and musculoskeletal systems.
• Somatosensation differs from senses like sight and hearing.

Why Somatosensation Matters

• Understanding competence/integrity of the nervous system aids patient/client management.
• It helps assess sensory loss extent, especially in nerve roots and peripheral nerves.
• It helps gather data on spinal tracts and brain function.
• Somatosensory exams assist in diagnosis and provide prognostic information.
• They give direction for intervention and evaluate/document sensory recovery.
• Sensation plays a key role in movement by guiding motor responses based on context and environment.
• They adapt movements and shape motor programs through feedback for corrective action.
• It enables feedback and feedforward mechanisms, while providing protection.

Clinical Indications for Somatosensory Examination

• Include risk Factors, health/wellness needs, pathology/health conditions, impairments, and activity limitations

Finding Indications for Somatosensory Issues

• Indications may surface during history taking, when addressing primary concerns, associated symptoms, review of systems, medical history, and functional limitations.
• They also appear during systems review like observation, strength screen, reflexes and dermatomal screens.

Sources and Effects of Sensory Dysfunction

• Sensory dysfunction can originate from peripheral nerve damage, trauma, impingement or compression, spinal cord injury, burns.
• Additional sources are toxins(chemotherapy, mercury, lead) and brain diseases(MS, ALS.
• It can also come from infections (Lyme disease, shingles, HIV), metabolic issues(diabetes, thyroid issues), CVA, and nutrition (B12 deficiency).
• Sensory dysfunction effects include difficulty standing, gripping, manipulating objects, and increased risk of injury.

Anatomy and Sensory Receptors

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

Types of Sensory Receptors

• Mechano-receptors identify mechanical deformation.
• Thermo-receptors respond to temperature.
• Noci-receptors register pain.
• Chemo-receptors detect chemical substances.
• Photic receptors sense visible light.

Levels of Sensory Receptors

• Superficial sensation involves exteroceptors providing info from external sources related to pain, temp, light touch pressure.
• Deep sensation involves proprioceptors providing info from muscles, tendons, ligaments, joints, fascia: position sense, joint resting position, movement, vibration.
• Combined cortical sensations require is info from both to enable stereognosis, 2-point discrimination, barognosis, graphesthesia, tactile localization, texture, and double simultaneous stimulation.

Anatomy of the Nerves

• Spinal cord gives rise to nerve roots, spinal nerves, plexus and peripheral nerves that feed into sensory receptors.

Dorsal Column System Anatomy

• Characterized by dorsal column-medial lemniscal tract.
• Fibers are large in diameter and rapid conducting.
• Sensation types include fine, discriminative touch and pressure, proprioception, and vibration.

Spinothalamic Tract Anatomy

• Characterized by anterolateral spinothalamic tract.
• Fibers are small and slow conducting.
• Sensation types include pain, temperature, crude, and non-discriminative light touch and pressure.

Somatosensory Cortex Function

• Areas with high sensitivity, like the feet, hands, and face, have more representation.
• It processes to determine initial position before movement, detect errors during movement, and identify movement outcomes.

Sources of Sensory Dysfunction

• The CNS, including brain, nuclei, spinal cord, and tracts can exhibit stroke and MS. Spinal cord lesions can trigger sensory dysfunction.
• The PNS, including spinal nerves, peripheral nerves, and sensory receptors can exhibit compression/cut/crush, radiculopathy/neuropathy and burn.

Types of Nerve Injuries

• Myelopathy, nerve root avulsion, radiculopathy, plexopathy, neuropathy, mononeuropathy, polyneuropathy, double crush, and neural tension can disrupt sensory function.
• Peripheral nerve injuries can be compression, blunt trauma, stretch, avulsion, severing, and disease.
• Wallerian degeneration involves myelin and axons degenerating distal to the site of nerve injury: Acute response to injury, lag between injury and onset of Wallerian degeneration, and execution of Wallerian degeneration.

Peripheral Nerve Injury Classifications

• Neuropraxia: A transient physiological block due to ischemia or stretch, without Wallerian degeneration, resulting in pain, muscle weakness, numbness and proprioception affected. Recovery time is minutes to days.
• Axonotmesis: Nerve architecture is preserved but axons are damaged to the point that Wallerian degeneration occurs, presenting pain, muscle wasting evident, complete motor, sensory and sympathetic functions lost. Recovery takes months. Sensation is restored before motor function.
• Neurotmesis: Nerve structure is destroyed, resulting in no pain, muscle wasting, complete motor, sensory and sympathetic function lost, and recovery takes months with surgery.

Somatosensory Examination Process: Subjective/Objective

• Subjective symptoms like numbness or tingling suggest formal sensation testing. Medical history and review of the neurological system is important.
• Objective indicators includes impaired light touch or motor screens, diminished reflexes point to need for formal testing.

Somatosensory Tests

• Testing depends on the established goal be it dermatome or peripheral nerve sensory distribution, superficial or deep sensors, a particular tract, or somatosensory cortex function.
• Multiple available tests that cover include touch awareness, pain perception, temperature, kinesthesia/proprioception awareness, vibration perception, stereognosis, tactile localization, two-point discrimination, double simultaneous stimulation, graphestesia, texture recognition, and barognosis.

Therapist Preparation

• Knowledge of anatomy/patterns and practicing consistent test delivery is paramount for a therapist.
• Required equipment includes tools, marking pencils, documentation and vision occlusion materials.

Touch Awareness Tools

• Camel hair brush, cotton swab or ball, tissue, and monofilaments can be leveraged to determine touch awareness.

Monofilament Tools

• Apply perpendicular to the skin, pressing until bent, for 1-2 seconds.
• 5.07 gauge/10 g = loss of protective sensation for the foot (plantar surface).
• ≤ 2.83 gauge/.07 g = normal sensation throughout most of the rest of the body

Applying Pressure/Monofilament

• Apply perpendicular to skin with a force to gauge when bent

Factors for Proper Patient Preparation/Examination

• Cognitively able, alert/oriented, appropriate age/maturity, ability to concentrate/focus, and tolerate testing.
• Testing environment should be quiet and free of distractions, with the patient place in relaxed position.
• Orientation involves demonstrating the test and what they are expected to feel.
• They must provide right "yes/no" to indicate sensation; avoid prompting. "Did you feel that?" is discouraged.
• The patient can indicate if what they feel is 'Sharp/Dull
• It is important to instruct that the must not guess to enhance reliability and validity. Focus if sensation is intact.
• Strategies: Vision occluded, disorganized variable/unpredictable vs controlled variable/unpredictable location, and cadence.
• Vary timing - but at least 2 seconds should be in between applications.

Examination Strategies

• Quick broad screen à specific area, occasionally in sensate area and remain aware or patient fatigue.
• Testing should be: "Bilaterally??? Distal to proximal??? Circumferentially???" Multiple trials for verification (x3/three).
• Map exact boundaries: Consider skin markers or image/chart

Other tests include...

• Pain(Sharp/Dull) and Localization.
• Double Simultaneous Stimulation (two points at once, not as detailed in mapping)
• Pressure(Be really cognizant about consistent pressure.

The Evaluation: What To Look For

• Patterns like dermatomes and peripheral nerve sensory distribution can be used in testing evaluation.
• You must reference with Myotomes and Motor nerve innervation.

Common Patterns of Sensory Loss

• CVA and Spinal Cord issues are based on location of infarct and injury
• MS is Unpredictable and Varied/Scattered
• Peripheral Neuropathy often stems from eg. Diabetes with Stocking and Glove results
• Spinal Nerve Root result in lots of overlap and Dermatome issues

Documentation

Documentation

• Type of sensation tested *Patient’s subjective and tool used responses and feelings
• Body surface affected about sensation change (specific - map) *Potential impact on
• Outcome: Degree/severity function Intact/Normal Scoring Absent
• 0, 1, 2, NT Impaired Diminished (Hyposensitive) *Percentage of right v

Testing Considerations

• Affected vs unaffected area, distal vs proximal, and variability(speed and location) helps create effective testing
• Remaining wary of fatigue and accuracy
• Sensory loss with motor loss indicates a neural lesion
• Neural lesions may take time to develop
• Check Possibility of "Double Crush" and Neural Tension

Intervention

• You can decide between Sensory Integration and/or Compensatory intervention.

Examination Case

• Median nerve vs C7 nerve root helps with differentiations.
• How do you differentiate weaknesses present