3.3 Sensory, Perceptual & Cognitive Screening
Key Takeaways
- Semmes-Weinstein monofilaments measure cutaneous light touch and protective sensation; threshold 2.83 indicates normal light touch, 3.61 diminished light touch, 4.31 diminished protective sensation, and 4.56 indicates loss of protective sensation (high ulcer/burn risk requiring visual compensation).
- Two-point discrimination assesses tactile gnosis and digital nerve innervation density, with normal static threshold defined as ≤5 mm (fair: 6–10 mm, poor: 11–15 mm).
- Homonymous hemianopia is a visual sensory field cut where clients demonstrate compensatory head scanning, whereas unilateral spatial neglect is an attention/perceptual deficit characterized by lack of awareness (anosognosia) and disorganized visual search.
- The Montreal Cognitive Assessment (MoCA, 30 points, cutoff <26) provides sensitive screening for mild cognitive impairment, evaluating executive function, memory, language, and visuospatial skills.
- The Allen Cognitive Level Screen (ACLS-5) evaluates functional cognition and learning capacity via leather lacing stitches: Running Stitch = Level 3 (Manual Actions), Whipstitch = Level 4 (Goal-Directed Actions), and Single Cordovan = Level 5 (Exploratory Actions).
Sensory, Perceptual & Cognitive Screening
Sensory, perceptual, and cognitive capacities form the neurological foundation for safe and independent occupational performance. Certified Occupational Therapy Assistants (COTAs), under OTR supervision, administer standardized screening tools to assess cutaneous sensibility, tactile discrimination, visual field integrity, spatial awareness, and cognitive processing.
1. Cutaneous Sensory Evaluation: Semmes-Weinstein Monofilaments
Semmes-Weinstein Monofilaments (pressure aesthesiometry) evaluate tactile thresholds using calibrated nylon filaments that bend at specific gram forces. It is the gold standard for detecting peripheral nerve compression (e.g., Carpal Tunnel Syndrome) and diabetic peripheral neuropathy.
Standardized Administration Protocol:
- Environment: Quiet room; client seated comfortably with hand fully supported on a putty or foam pad.
- Vision Occlusion: Client's vision is occluded (shield or blindfold).
- Application Technique: Apply filament perpendicular ($90^\circ$) to the skin surface until the filament bows/bends into a C-shape. Hold bowed for 1.5 seconds, then lift for 1.5 seconds.
- Trials:
- For filaments 1.65 through 4.08: Apply up to 3 times per site; 1 positive response confirms perception.
- For filaments 4.17 through 6.65: Apply 1 time only per site.
- Testing Progression: Begin with the thinnest filament ($2.83$) and progress distally to proximally across median, ulnar, and radial nerve distributions.
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| SEMMES-WEINSTEIN MONOFILAMENT THRESHOLD SCALE |
| |
| [2.83 GREEN] ---> NORMAL LIGHT TOUCH |
| Intact tactile sensation; normal fine motor skills. |
| |
| [3.61 BLUE] ---> DIMINISHED LIGHT TOUCH |
| Fair stereognosis; good recovery after nerve repair. |
| |
| [4.31 PURPLE] ---> DIMINISHED PROTECTIVE SENSATION |
| Can feel pain/temperature; poor texture discrimination.|
| |
| [4.56 RED] ---> LOSS OF PROTECTIVE SENSATION (CRITICAL WARNING) |
| Cannot feel injury/pinprick; high burn/ulcer risk! |
| *Requires mandatory visual compensation training.* |
| |
| [6.65 ORANGE] ---> DEEP PRESSURE SENSATION ONLY |
| Perceives only heavy somatic pressure / bone vibration.|
| |
| [>6.65 BLACK] ---> ABSENT SENSATION (ANESTHETIC) |
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Monofilament Thresholds & Clinical Implications
| Monofilament Size | Force (Grams) | Clinical Classification | Sensory Status & Safety Considerations | | :--- | :--- | :--- | :--- | :--- | | 1.65 – 2.83 | $0.008 - 0.068\text{ g}$ | Normal Light Touch | Normal cutaneous sensation; intact light touch, two-point discrimination, and stereognosis. | | 3.22 – 3.61 | $0.166 - 0.408\text{ g}$ | Diminished Light Touch | Mild sensory loss; perceives light touch but may have difficulty with fine texture discrimination. | | 3.84 – 4.31 | $0.692 - 2.04\text{ g}$ | Diminished Protective Sensation | Sensation impaired; can feel sharp pain and hot/cold, but vulnerable to microtrauma. | | 4.56 | $3.63\text{ g}$ | Loss of Protective Sensation | High clinical risk. Client cannot detect cuts, blisters, or thermal burns. Mandatory safety education (visual skin checks, water temperature testing). | | 6.65 | $447\text{ g}$ | Deep Pressure Sensation | Client feels only heavy, deep pressure; superficial skin is anesthetic. | | $> 6.65$ | $> 447\text{ g}$ | Absent Sensation | Total numbness; no perception of deep pressure or mechanical stimuli. |
2. Tactile Discrimination: Two-Point Discrimination
Two-point discrimination evaluates tactile gnosis and the innervation density of digital mechanoreceptors. It is commonly measured using a Disk-Criminator or Mackinnon-Dellon calipers.
1. Static Two-Point Discrimination (Dellon / Weber)
- Protocol: Vision occluded. Two blunt prongs applied simultaneously along the longitudinal axis of the digit pulp with light pressure (just blanched skin) without movement.
- Scoring: The client must correctly identify 1 versus 2 points on 7 out of 10 trials at a given distance.
- Standardized Diagnostic Norms:
- Normal: $\le 5\text{ mm}$
- Fair: $6\text{ mm to } 10\text{ mm}$
- Poor: $11\text{ mm to } 15\text{ mm}$
- Protective: 1 point perceived only
- Anesthetic: Zero points perceived
2. Moving Two-Point Discrimination (Dellon)
- Protocol: Prongs moved longitudinally from proximal to distal along the digit pulp. Normal threshold is $2\text{ mm to } 3\text{ mm}$. Moving two-point discrimination recovers weeks to months before static two-point discrimination following digital nerve laceration and repair.
3. Visual Fields vs. Unilateral Spatial Neglect
Following stroke or traumatic brain injury, distinguishing between an optical/sensory visual field cut and a higher-order perceptual inattention/neglect deficit is critical for selecting intervention strategies.
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| VISUAL FIELD CUT VS. UNILATERAL SPATIAL NEGLECT |
| |
| [HOMONYMOUS HEMIANOPIA (FIELD CUT)] [UNILATERAL SPATIAL NEGLECT] |
| • Optical/sensory tract deficit • Attentional/perceptual |
| • Damage to optic radiation / occipital neurological deficit |
| • CLIENT IS AWARE of missing visual field • Damage to right parietal/ |
| • Organizes systematic head & eye turns frontal cortex |
| • Normal visual search patterns • CLIENT IS UNAWARE of deficit|
| • Reads using finger tracking anchors (Anosognosia) |
| • Fails to search left side |
| • Disorganized visual scan |
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Comparison & Screening Tools Matrix
| Clinical Dimension | Homonymous Hemianopia (Field Cut) | Unilateral Spatial Neglect (Inattention) |
|---|---|---|
| Pathology | Lesion in optic tract, lateral geniculate nucleus, optic radiation, or visual cortex (V1). | Lesion in right inferior parietal lobe, temporoparietal junction, or frontal eye fields. |
| Client Awareness | Intact (Aware): Client notices dark/blind area; reports bumping into objects on that side. | Impaired (Anosognosia): Client is unaware of the neglected side and denies any deficit. |
| Compensatory Saccades | Spontaneous, organized visual search toward the blind field; client rotates head to compensate. | Restricted, erratic saccades concentrated entirely within the intact ipsilateral visual field. |
| Reading Performance | Slowed reading speed due to losing place on text line; benefits from visual anchor line. | Omits words on left half of the page; does not realize words or letters are missing. |
| Screening Tools | • Confrontation Testing: Client looks at examiner's nose while peripheral targets are moved into quadrants. | • Line Bisection Test: Client bisects lines significantly skewed to the right.<br>• Clock Drawing Test: Numbers crowded on right half; left half blank.<br>• Albert's Test / Letter Cancellation: Omits targets on left. |
4. Standardized Cognitive Screening: MoCA & MMSE
Cognitive screening tools provide standardized, rapid detection of cognitive impairment to guide referral, safety precautions, and occupational therapy interventions.
1. Montreal Cognitive Assessment (MoCA)
- Overview: 30-point standardized screening instrument designed to detect Mild Cognitive Impairment (MCI) and early dementia.
- Domains Assessed:
- Visuospatial / Executive (5 pts): Alternating Trail Making (1 pt), 3D Cube Copy (1 pt), Clock Drawing Test (contour 1 pt, numbers 1 pt, hands 1 pt).
- Naming (3 pts): Lion, Rhinoceros, Camel.
- Memory / Delayed Recall (5 pts): 5-word delayed verbal recall after short delay.
- Attention (6 pts): Forward digit span (1 pt), Backward digit span (1 pt), Vigilance tapping on letter 'A' (1 pt), Serial 7 subtractions from 100 (3 pts).
- Language (3 pts): Sentence repetition (2 pts), Phonemic letter fluency ($\ge 11$ words starting with 'F' in 60s, 1 pt).
- Abstraction (2 pts): Conceptual similarities (e.g., train/bicycle, watch/ruler).
- Orientation (6 pts): Date, month, year, day, place, city.
- Scoring & Cutoff:
- Education Correction: Add $+1\text{ point}$ if client has $\le 12\text{ years}$ of formal education (max score remains 30).
- Cutoff Score: $\ge 26 / 30$ is normal; $< 26$ indicates cognitive impairment / MCI.
2. Mini-Mental State Examination (MMSE)
- Overview: 30-point tool assessing orientation, immediate registration, attention/calculation (serial 7s or spelling "WORLD" backwards), recall, and language/praxis.
- Cutoff Score: $< 24 / 30$ indicates cognitive impairment. Less sensitive to mild cognitive impairment and frontal executive deficits than the MoCA.
5. The Allen Cognitive Level Screen (ACLS-5) & Cognitive Disability Model
The Allen Cognitive Level Screen (ACLS-5) and Large LACLS-5 utilize a standardized leather lacing task to evaluate functional cognition, learning capacity, and problem-solving abilities within Claudia Allen's Cognitive Disability Model.
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| THE ACLS-5 LEATHER LACING STITCHES |
| |
| [STITCH 1: RUNNING STITCH] ---> Evaluates LEVEL 3 (MANUAL ACTIONS) |
| • Over-and-under manual stitch. Client grasps & manipulates objects|
| • Client must replicate 3 stitches. repetitively; tactile cues only. |
| |
| [STITCH 2: WHIPSTITCH] ---> Evaluates LEVEL 4 (GOAL-DIRECTED) |
| • Loops over leather edge. Client completes visible goals; |
| • Includes Cross-over & Twist errors. corrects visible errors. |
| |
| [STITCH 3: SINGLE CORDOVAN] ---> Evaluates LEVEL 5 (EXPLORATORY) |
| • Complex multi-step loop stitch. Client uses trial-and-error |
| • Evaluates inductive problem solving problem-solving; new learning. |
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Detailed Hierarchy of Allen Cognitive Levels (ACL 1 through 6)
| Allen Level | Name & Focus | Key Behavioral Characteristics | Functional ADL/IADL Capacity & Supervision Needs |
|---|---|---|---|
| Level 1 | Automatic Actions<br>(Arousal / Reflexive) | Responds to internal sensory cues; fleeting attention (seconds); reflexive swallowing/turning. | Total 24-hour nursing care. Bed-bound; dependent in all ADLs. |
| Level 2 | Postural Actions<br>(Gross Body Movement) | Motivated by comfort and gravity; walks/wanders; righting reactions; copies gross motor postures. | 24-hour supervision to prevent wandering and falls. Can assist with simple ADLs (e.g., holding arm out for sleeve). |
| Level 3 | Manual Actions<br>(Repetitive Tactile) | Uses hands to touch and manipulate tactile objects; repetitive actions; unaware of cause-and-effect; 30-min attention span. | 24-hour supervision and setup. Performs familiar grooming/eating steps with tactile cues. Needs supplies placed directly in front of them. |
| Level 4 | Goal-Directed Actions<br>(Visual Cues / Routines) | Can sequence visible steps to complete a familiar goal; recognizes visible errors; cannot correct hidden errors; 1-hour attention. | Lives in supportive living / requires daily supervision. Independent in basic self-care with visual cues. Cannot manage finances, medications, or unexpected emergencies. |
| Level 5 | Exploratory Actions<br>(Trial-and-Error / Inductive) | Overt trial-and-error experimentation; learns new tasks; impulsive; poor anticipation of safety hazards. | Independent living with periodic check-ins. Independent in basic ADLs; needs assistance with complex IADLs (finances, budgeting, safety planning). |
| Level 6 | Planned Actions<br>(Conceptual / Deductive) | Abstract reasoning; covert mental trial-and-error; anticipates problems and plans safety precautions. | Fully independent. Capable of independent living, employment, and novel problem-solving without supervision. |
6. Clinical Scenario: COTA Administering Cognitive & Sensory Screening
Clinical Case Vignette: A 74-year-old client with vascular dementia and a history of right middle cerebral artery (MCA) stroke is admitted to a subacute rehabilitation unit. The supervising OTR asks the COTA to administer the Semmes-Weinstein sensory screen on the left hand, conduct visual neglect screening, and administer the ACLS-5 leather lacing assessment.
COTA Screening Process & Observations:
- Sensory Screen (Semmes-Weinstein): On the left palmar median nerve distribution, the client fails to respond to filaments $2.83, 3.61,$ and $4.31$, but responds to the $4.56$ filament. The COTA records Loss of Protective Sensation and initiates visual skin inspection education.
- Neglect Screening (Clock Drawing): The client draws a circle and crowds all 12 numbers onto the right half of the circle, leaving the left half entirely blank, indicating unilateral spatial neglect.
- ACLS-5 Administration:
- Running Stitch: Client completes 3 running stitches independently.
- Whipstitch: Client completes whipstitches and corrects a twisted lace when pointed out visually, but fails to identify or correct a hidden cross-over error on the back.
- Single Cordovan: Client cannot deduce the single cordovan stitch and refuses trial-and-error.
- Outcome & Level Assignment: Performance corresponds to Allen Cognitive Level 4.0 to 4.2 (Goal-Directed Actions).
- Intervention Recommendations to OTR: The COTA reports that the client requires high-contrast visual cues, structured routines, and daily supervision for ADL safety, along with visual scanning training for left neglect.
A COTA is administering a Semmes-Weinstein monofilament sensory evaluation on the volar surface of a client's hand. The client does not perceive the 2.83, 3.61, or 4.31 filaments, but consistently detects the 4.56 filament. What is the clinical classification of this sensory threshold and what is the primary clinical safety implication?
During a static two-point discrimination screening on the index fingertip following a digital nerve repair, the client correctly identifies two distinct points at 4 mm on 8 out of 10 trials. How should the COTA categorize this finding according to standardized norms?
A client who recently sustained a right hemisphere cerebrovascular accident presents with visual deficits. When asked to draw a clock, the client places all twelve numbers crowded onto the right side of the clock face and does not realize the left side is completely empty. When reading, the client starts in the middle of lines and does not turn the head to look left unless physically prompted. What condition is primarily indicated by these screening findings?
During the administration of the Allen Cognitive Level Screen-5 (ACLS-5), a client successfully completes the running stitch (Level 3) and completes the whipstitch, recognizing and untwisting a twisted lace. However, when the client encounters a mistake on the back of the leather and cannot see it from the front, the client fails to inspect the back and cannot complete the single cordovan stitch. Which Allen Cognitive Level corresponds to this performance?