Interrupting the damaging downward spiral of desensitization, weakness and pain
As I described in my article “The Four Pillars of Hand Therapy” [ADVANCE, May 2016], sensation is an important consideration when treating hand injuries.
While edema, scar management, range of motion and strength are the four pillars, we must have a foundation on which to improve hand function. That foundation is sensation. Without sensation in the hands, we limit their use, protect the area or extremity, and slowly lose functional use of that limb.
Sensory limitations can be caused by carpal and cubital tunnel syndrome, surgical complication, and physiological response to surgery, including edema and excessive collagen production causing heavy scar tissue, among other origins.
Therapists primarily confront two types of sensation dysfunctions: hyposensitivity and hypersensitivity. Both are problematic in their own way, and both require education and rehabilitation to return the patient to the highest level of function. With sensation insults, we often see texture discrimination issues, stereognosis concerns, and diminished protective sensation including hot and cold sensation and touch-pressure threshold detection levels.
According to Burke, upper-extremity impairment secondary to sensory or pain interference has five levels.1 Grade 4 presents with diminished light touch, which includes good-to-fair two-point discrimination along with good protective response and minimal abnormal pain.
Grade 3 includes protective sensation but increased abnormal pain and mislocalization of sensory input. Grade 2 includes decreased protective response; hand function declines at this point. Weakness is also present at this level. Mislocalization and/or over-responsiveness is present, which will start to impact function. Two-point discrimination is further diminished at this level.
Grade 1 is characterized by deep pressure sensibility with limited hand function. The patient is unable to function outside of line-of-sight, indicating heavy compensation with vision. Pain levels are severe. Grade zero presents with a non-functional, asensory hand with severe pain.
Assessment of Function and Sensation
Function and sensation have a direct correlation, as outlined in the grades above. As sensation declines and awareness of the decline increases, we reduce the use of our hands and extremities. This causes a downward spiral effect as weakness further impairs function. Along with diminished sensation comes pain, which exacerbates the weakness and functional decline.
Using questionnaires such as the DASH or QuickDASH will provide a snapshot of what the client feels he’s experiencing from a functional standpoint. During evaluation and treatment planning, it’s important to compile a complete picture of sensation, which will help complete the picture of function, along with the questionnaire and interview processes.
A combination of assessments is most beneficial, such as monofilaments with a clear grade scale to identify deficits, two-point discrimination, and moving two-point discrimination with informal testing techniques such as touch pressure (similar to monofilament test)or trial-based sensation testing.
Nerve regeneration at approximately 1 mm per day or 1 inch per month can be very slow, which makes retesting extremely important to identify client progress. This will improve patient morale as well as support reimbursement.
As with any other injury or insult to the body, the severity of the injury will directly impact the potential for healing. According to Meriano et al., “The degree to which a sensory program is successful relies heavily on frequency.”2Education and a well-established home exercise program are paramount to return the highest level of independence.
Hyposensitivity
Also known as anesthesia, hyposensitivity requires re-education. The most commonly accepted techniques are those outlined by Dellon (evaluation of sensibility and re-education of sensation in the hand). These techniques are generally described as discriminative sensory re-education.
Discriminative sensory re-education focuses on training to remind the system of how movement feels, using vision to see and provide feedback and compensation. This should be graded as progress develops with the ultimate goal of successful completion of activities with vision occluded, with gross-motor sensation returning first.
Protective sensory re-education is vital, with an emphasis on safety training, avoiding repetitive activity for a long period of time, and built-up handles on objects such as forks, knives and other utensils when possible. Decreasing the amount of force used when gripping and proper skin care, including moisturizing to prevent drying and cracking, are also recommended.
Sensory re-education can be classified into two phases. Early-phase sensory re-education should be initiated when the patient can feel vibration of 30 cycles per second (CPS) using a tuning fork, and will progress toward 256 CPS, which would be the highest level of sensation.
Dellon describes two stages, the first state being “submodality-specific perceptions, movement vs. constant-touch and pressure.” The second focuses on correction of misdirection, as well as localization limitations.
The late phase should be initiated as moving-touch and constant-touch begins to be perceived with good localization at the fingertips. Dellon states that it’s never too late to begin late-phase sensory re-education, but starting too early leads to client failure and can have negative impacts.
Generally this phase begins between week 6 and 8 months with injuries at the wrist. It’s also important that sensory re-education does not induce axonal regeneration, but facilitates maximum potential from nerve repairs.
Hypersensitivity
Hypersensitivity can be broken down into two categories. Hyperesthesia is increased sensitivity and paresthesia is abnormal or misinterpreted sensation.
These conditions can be addressed through immersion bins and dowel and wand techniques. Other methods of gradation can begin with a softer sensation and move to more abrasive media. This will gradually desensitize the concerned area, which in effect returns the area to normal sensory reception. This treatment is ultimately uncomfortable at best, which makes adherence to home programs more difficult, and patient education a priority.
Emerging Research
Not much has changed in the way of sensory re-education. Peripheral nervous system (PNS) injuries are re-educated in a similar manner to central nervous system injuries, and these techniques overlap in cases of TBI and stroke rehabilitation.
When treating PNS insults such as cubital tunnel syndrome or other insults to the radial, ulnar and median nerve, keep in mind what sensation deficits your patients are experiencing and consider the possibility they’re experiencing both in different areas — for example, hyposensitivity in the fingertips with hypersensitivity at or near the surgical site.
Keeping up with new research and emerging treatment techniques such as cortical reorganization, and incorporating this into our treatment planning, will provide patients the best opportunity to maximize functional independence.
