Hypertonia Assessment Tool

Original Editor - Lauren Heydenrych

Top Contributors - Lauren Heydenrych and Kirenga Bamurange Liliane  

Objective[edit | edit source]

The Hypertonia Assessment Tool (HAT) is a standardized clinical tool used to identify different forms of hypertonia in the paediatric population. These subtypes include:

There are several scales that measure the severity of hypertonia, but up until the HAT, none differentiated between the forms of hypertonia. This is important to identify as different forms of hypertonia are managed differently, including medically (in terms of drug prescription) and surgically. With regards to research, being able to identify subtypes of hypertonia enables better specificity with patient recruitment and outcome reporting.[1]

Intended Population[edit | edit source]

The HAT is administered to children between 4 to 19 years of age. These children should demonstrate hypertonia in at least one limb.[2] Hypertonia is defined as “abnormally increased resistance to externally imposed movement about a joint”[1] In the HAT user manual it puts it as “increased resistance to passive stretch of a muscle”.

Tool description[edit | edit source]

The HAT is a seven-item scoring tool. These 7 items comprise of 2 spasticity items, 2 rigidity items and 3 dystonia items. These 7 items are recorded for each of the affected limbs.

Equipment required[edit | edit source]

  1. HAT scoring chart (one sheet for each limb being tested)
  2. Pen/ pencil to record scoring
  3. Examination table for child/youth to lie down on.

Set-up[edit | edit source]

The child or youth should lie supine on the examination table/ support surface. The child should be wearing unrestrictive clothing and the hand or foot of the limb being tested bare. If possible, hands should be placed gently on their upper abdomen. A roll should be placed under the knees and a pillow under the head.

Method of Use[edit | edit source]

Before commencing administration of the HAT it is recommended to review the HAT user manual.

During the assessment, the evaluator moves a child’s limb in a series of purposeful stretches and movements.

The movement itself is observed, as well as increased tone and/or resistance.

These 7 items include:

  1. Increased involuntary movements or postures of the designated limb with tactile stimulus of another body part.
  2. Increased involuntary movements or postures with purposeful movement of another body part.
  3. Velocity dependent resistance to stretch.
  4. Presence of a spastic catch.
  5. Equal resistance to passive stretch during bi-directional movement of a joint.
  6. Increased tone with movement of another body part.
  7. Maintenance of limb position after passive movement.

The test takes approximately 5 minutes per limb tested.

Scoring and interpretation[edit | edit source]

The presence of at least one HAT item per hypertonia subgroup (Spasticity, dystonia or rigidity) confirms the presence of the specific hypertonia.

If a child scores in more than 1 hypertonia subgroup, mixed tone is present.

Scoring is divided into 0 or 1. With 0 designated as an absence of the movement abnormality and 1 to a positive identification of the movement abnormality.


Evidence[edit | edit source]

Individual item validation, Inter-Rater reliability, Test-Retest Reliability and Criterion Validity was performed during the initial formation and testing of the HAT.[1] 25 children (diagnosed with cerebral palsy) were recruited for the study. They were examined by three independent physicians (blinded to each other’s scores). Two administered the HAT, while the third administered a paediatric neurological examination. After 2 weeks the same children were re-examined using the HAT.

A study performed by Knights et al. (2013) found that videotaping the test being performed did not significantly change the outcome of the scoring. Dystonia, item 1 however, did not change the HAT hypertonia diagnosis and was removed from the HAT.[4]

Reliability[edit | edit source]

In the initial formation of the HAT test test-retest reliability was reported as excellent for spasticity (1.0), for dystonia only moderate (0.43) and for the absence of rigidity excellent (0.91-1.0). Interrater reliability was substantial (0.65) for spasticityy, fair for dystonia (0.3) and excellent for the absence of rigidity (0.91-1.0) .[1]

In a study performed in 2016 - using 2 physicians and 45 children - interrater reliability (n=45 ) of the HAT subtypes was moderate to substantial. Intrarater reliability (n=42) was almost perfect.[5]It must be noted that this study took participants diagnosed with neuromotor disorders and not strictly cerebral palsy.

Validity[edit | edit source]

When looking at validity, the initial study reported moderate to good (0.57-0.74) validity for spasticity, mixed readings for dystonia (ranging from fair to substantial) (0.3-0.65) and for the absence of rigidity, all readings were excellent (0.91-1.0).[1]

In the 2016 study, validity for the HAT in testing spasticity was confirmed, whereas it was advised that further studies were needed to ascertain validity for dystonia and rigidity.[5]

Links[edit | edit source]

To access the free downloadable scoring sheet click here.

To access the free user manual you need to register on the Holland Bloorview Kids Rehabilitation Hospital site here.

References[edit | edit source]

  1. 1.0 1.1 1.2 1.3 1.4 Albright L, Andrews M. Development of the hypertonia assessment tool (HAT). Developmental medicine and child neurology. 2010 May 1;52(5):411.
  2. Fehlings D. Switzer L. Jethwa A. Mink . Macarthur C. Knights S. Fehlings T. Hypertonia Assesment Tool (HAT) User Manual. 2nd Edition. Bloorview Children’s Hospital Foundation and the National Institutes of Health. 2017.
  3. Dr. Darcy Fehlings. Research CP Dystonia Edition Webinar #2 A Care Pathway for Dystonia. Available from: https://www.youtube.com/watch?v=o9RUBnu8V4w [last accessed 28/6/2022]
  4. Knights S, Datoo N, Kawamura A, Switzer L, Fehlings D. Further evaluation of the scoring, reliability, and validity of the Hypertonia Assessment Tool (HAT). Journal of Child Neurology. 2014 Apr;29(4):500-4.
  5. 5.0 5.1 Marsico P, Frontzek-Weps V, Balzer J, van Hedel HJ. Hypertonia assessment tool: reliability and validity in children with neuromotor disorders. Journal of child neurology. 2017 Jan;32(1):132-8.