Tone: Striking a Balance to Maximize Function

The Challenges of Hypotonicity

Hypotonia is like love: It’s hard to define, but you know it when you feel it! Recognizing low tone requires a person who knows how to feel “floppy” and how to see the clinical signs of decreased resistance to passive movement and decreased tonic contraction of antigravity muscles. Therapists often describe this as a decreased state of “readiness” for movement. What we see functionally is impairment of the ability to sustain postural control and movement against gravity, producing a delay in motor development with abnormal patterns of movement.

Why & When Hypotonicity Happens

According to a leading expert, Dr. Andrew Morgan from Peoria, Ill., the symptoms and signs of hypotonia include:

  • Head lag on pull-to-sit
  • Slip-through at the shoulders
  • Poor trunk extension
  • Astasis in supported standing
  • Decreased resistance to flexion/extension of the extremities
  • Exaggerated hip abduction
  • Exaggerated ankle dorsiflexion

Physical and occupational therapists typically assess children with hypotonia using standardized gross motor testing. In this population, since no assessment exists that is tailored to this diagnosis, it is important to use a qualitative checklist that would include descriptions of the following typical findings and patterns:

  • W-sitting
  • Combat crawl
  • Wide-based gait
  • Genu recurvatum
  • Foot pronation
  • Poor head control
  • Limited weight-bearing
  • Poor stability when weight-bearing
  • Impaired mobility
  • Oral-motor dysfunction
  • Poor respiratory support
  • GE reflux

When a therapist is assessing a child and suspects hypotonia, a physician should be consulted to identify the cause. The physician’s differential diagnoses list might include:

  • Anterior horn cell (spinal muscular atrophy)
  • Neuromuscular transmission (myasthenia gravis, botulism)
  • Muscle fiber (myotonic dystrophy, congenital myopathies, muscular dystrophy)
  • Genetic disorders (Down, Prader-Willi, Fragile X, Sotos, and Rett syndromes)

The physician would most likely question the family about relatives with similar illnesses/diagnoses, and whether the child has a history of respiratory difficulty; significant limitation of movement; “mushy” muscles; muscle atrophy; significant weakness; decreased deep tendon reflexes; myotonia; and/or fasciculations.

Hypotonia Types & Differences

Dr. Morgan describes three patterns of hypotonia: transient, minimal impairment and globally delayed.

The majority of the children we see have central hypotonia versus peripheral causes. Central hypotonia is an impairment of the ability to sustain postural control and movement against gravity, “reflective of a more generalized inefficiency of brain processing and organization.” The motor impairment is typically accompanied by additional deficits in cognition, behavior and neurological function.

If this hypotonia is transient, it will resolve over time, and the child’s motor skills “normalize” between 9 and 18 months. Usually, the child will be able to demonstrate independent ambulation by 18 months. The motor coordination can be variable, but no significant deficits are usually present.

Strubhar, et al., surveyed 105 parents of children diagnosed with hypotonia. Only 10.5 percent of the children had their hypotonia resolve (transient). Even the group with minimal impairment (32.4 percent) had mild problems such as learning disability or language delay, but no major developmental diagnosis. A globally impaired group (40.9 percent) had mental retardation or a recognizable genetic/developmental diagnosis. More than 50 percent of the minimal impairment group had poor coordination, language delay and learning difficulties. The mean walking age (minimal group) was 22 months. Initial fine motor and cognitive, but not gross motor, developmental quotients were significantly greater in the minimal group compared to the global impairment group. This really means that the deficits in motor coordination, language and learning difficulties were common problems that persisted in the minimal and global impairment groups. Almost 90 percent of the children had persistent impairments that could be helped with early intervention.

Assistive Technology Interventions

One of the hallmarks of hypotonia is poor trunk control. While some clinicians describe this as weakness, the impact on function comes from the lack of stability.

To help the child compensate and learn what stability feels like, trunkal compression garments can be used. Benik, Spio, Theratogs, and Dynamic Motion Orthosis all make custom garments that can assist people with hypotonia. In addition, there are now at least three published articles suggesting that orthotics improve gait in children and teens with Down syndrome.

In the last few years there has been an explosion of positioning devices designed for children with movement disorders (dystonia, athetosis), extensor patterns and hypotonia. The principle here is that movement helps the brain to learn, while static sitting does not. Most clinicians believe that stability is better for function (like using an augmentative communication device or self-feeding), but for the other three to four hours a day, a “dynamic” system may help the brain learn to normalize the movement patterns.

Snug Seat and R82 (the parent company in Denmark) added a spring-loaded back to the Panda seat and gave us the X:Panda. This allows for hip extension, and then the seat gently brings the child back toward neutral. At the International Seating Symposium, a group of Italian researchers – Avellis, et al. — presented an excellent study on 10 children with CP. The study compared them with the X:Panda locked out and in the “dynamic” condition. The findings were remarkable in that the children exhibited less extensor thrust in the dynamic configuration. There was also less “sliding” of the pelvis and posterior pelvic tilt in the dynamic or active condition. The movement patterns were smoother (less “jerk”) and less forceful in the active configuration. For the children with dystonia, the excursion of their movements actually decreased.

Sunrise Medical distributes the Kids ROCK and BINGO (early- intervention) systems. Kids ROCK allows movement at the hip and knee. The unique extension mechanism allows the seat to follow the pelvis through the flexion extension cycle and keeps the ischial tuberosities in the “sweet” spot. Hahn, et al., published a study looking at 12 children with neuromuscular dysfunction with the system locked out and in its active configuration. The children who were able to move showed improvement in the standing and walking domain of the GMFM, while the children in locked-out systems improved in sitting and lying. All of the children who were able to move showed a trend toward more normal spasticity — meaning the hypotonic kids got more tone, and the hypertonic kids got less tone.

The Twist system from Thomashilfen and Exomotion is the only one designed specifically for children with hypotonia. The system has small, pivoting, spring-loaded pieces that provide “micro stimulation” to deliver sensory information and prompt the child toward a more symmetrical, upright posture. This design is available in an early-intervention model, a pediatric version, a larger model for adults and even a bed! The families I have tried this system with report their children are happier, are more vocal, and move more.

Here is the message I am hoping to convey: Hypotonia is an important finding and, too often, is neither transient nor benign.We have many tools in our arsenal designed specifically to help children with hypotonia. When hypotonia is recognized early, we may be able to improve the expected outcome and allow children to function and participate more fully.

The Challenges of Hypertonicity

Q&A with Lois Brown, MPT, ATP & Sharon Pratt, PT

Hypertonicity – aka, “high” tone – “is usually describing a muscle that is under unusually high tension,” says Sharon Pratt, PT, director of clinical education for Sunrise Medical. As such, hypertonicity is seen in varying degrees in clients with cerebral palsy, multiple sclerosis, spinal cord injuries, cerebral vascular accidents (stroke), Parkinson’s disease and brain injury.

Although effects of hypertonicity occur in the muscles, the cause of excessive tone is in the brain, says Lois Brown, MPT, ATP, rehab clinical education specialist, Invacare Corp.

We consider this to be neurologic tone,” Brown explains. “Increased spasticity is generally described as an exaggerated contractile response to stretch. That’s the abnormal neurologic message. It’s damage to the central nervous system.”

So how do muscles act differently in a client with hypertonicity? “If I try to stretch the muscle too quickly and harshly, it’s going to actually contract more,” Brown says. If a person without hypertonicity were to, for instance, stretch his hamstrings, “(He) would hold it, and eventually it would stretch and the muscle would return to its original length.” But that’s not necessarily the case for someone with too much tone: “Sometimes if you stretch a passive muscle that has tone, it actually will make it contract more.”

Hypertonicity’s Exacerbating Factors

A wide range of other factors can further impact a client’s high tone. “Tone can be influenced by medication, excitement, stress and external environmental factors, to name a few,” Pratt notes. “For example, loud noise can cause startle, which can trigger tonal changes. We commonly see a child seated well in their system, when suddenly there is a loud, unexpected noise, and immediately the child is exhibiting hypertonicity in the extensor muscles, which causes them to extend out of the seated position.”

Brown says that injuries, illnesses and other physical conditions, such as fatigue, urinary tract infections (UTI), bowel impactions and even ingrown toenails, can temporarily increase tone. “There are clients that say they can tell by their tone or spasticity that they have a UTI,” she explains.

Ill-fitting seating & mobility systems can also increase tone. “A person who is not seated correctly — for example, whose postural needs have not been respected and accommodated — may be fighting the system constantly,” Pratt says. “This too can trigger hypertonicity.”

“Paramount to managing hypertonicity,” Brown says, “is excluding or reducing noxious stimuli, like a UTI, like a bowel impaction, any skin irritation or pressure ulcer (that) might change their tone or spasticity. Even something like a tight-fitting orthosis, like a legbrace or a clamshell, or an ill-fitting wheelchair.”

Keeping Tone Under Control

“It’s long-term management,” Brown says when asked the best strategy to deal with hypertonicity. Even after all those mitigating factors are identified and we try to treat them, (excessive tone levels) may fluctuate, but they’re not likely to resolve and just go away. You’re going to try to manage tone over the person’s life.”

Because tone varies from client to client, individual evaluations are critical to developing effective outcomes.

“The key for clinicians,” Pratt says, “is to be able to identify the triggers as well as the inhibitors of the hypertonicity and then to ask themselves whether the triggers can realistically be managed by the seating solution that is being proposed. For example, it is virtually impossible for a static seating solution to manage effectively a dynamic extensor posture when the extensor tone is being triggered by an external environmental factor or by excitement.”

“You need to get the individual out of the wheelchair and onto a mat, and watch what happens to their body,” Brown advises. “Do they actually relax, does a certain position cause (tone) to increase or decrease? What position allows them to have more isolated movement? Maybe the position they’re in in the chair actually precludes them from having more free-joint range of motion or active range of motion of any joint that might move. You can’t do a proper evaluation in the chair if that’s what’s setting off their tone.”

Brown adds that hypertonicity and its causes vary so much that what works for one client might not work for another.

“I have seen a guy who was in a custom-molded system that I wanted to sit him up more,” Brown says. “I closed the back angle 5 to 10 degrees, something very minimal in our terms. His mother called me the next day and said, ‘You need to open the back angle.’”

That relatively small modification to the wheelchair back had, in fact, severely worsened the client’s spasticity.

“We need to take away our concept of what is good posture for someone,” Brown says. “We only should base it on what is their most comfortable, most functional position: less pain, less tightness, what allows them to function better. You want to optimize his upright posture, but not so much so that he becomes so spastic and tight that he can’t relax, he’s not comfortable, he’s in pain, he can’t move.”

For some high-tone clients, Pratt notes, a little freedom to move can equal a lot more comfort and function.

“Seating cannot manage excitement,” she says. “This is typically the case where we see footrests and headrests being constantly broken and going out of alignment. The question always is — how many straps and contours will it take to hold the client in the system, and the result is that usually the body wins. This is when we see a terrific application of dynamic seating solutions for some clients. Instead of fighting the movement that is going to take place no matter what we do – allow the movement to happen without resistance, and allow a return to a safe seated position.”

Expect High Tone to Change

“Change is the name of the game when it comes to hypertonicity,” Pratt says. “The tone we see in clients’ muscles can change by the minute, hour, day and week. There is not necessarily consistency, especially in those persons where the triggers are environmental or emotion related.”

When tone is related to positioning – for instance, Pratt says, “’when the hip is in the open/more extended position, we notice the extensor tone increasing’ – then this can be a more consistent observation, and the solution may be a simple as closing the hip angle (flexing it) while maintaining a natural lumbar lordosis.”

But even in those cases, Brown says, providers should be careful to ask, during assessments, about factors that could impact hypertonicity.

For instance, a new anti-spasticity medication “could actually have a worsening effect on their function, because sometimes spasticity is being used for postural stability,” she says. “That muscle tightening around a joint gives them stability to maybe do a transfer. So if it changes the postural tone, it can exaggerate the weakness, and it can take away their ability to stand or to even walk. So there’s a very fine line there as far as balancing.”

That’s perhaps the most complex challenge of working with tone: Managing it as it changes, while maintaining enough to keep the client functional and comfortable.

“It seems like (hypertonicity is) bad, bad, bad, we have to get rid of it,” Brown says. “With some tone – obviously not the kind caused by UTIs, etc., but the rest of it – there’s a very fine line between what you should reduce or can reduce before you take away function. For certain individuals, it can provide them with function that they might not otherwise have.”

This article originally appeared in the September 2009 issue of Mobility Management.

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