Turkish Translation , Validity and Reliability of the Hypertonia Assessment Tool in Children With Motor Disorders

Among children with omotor disorders, particularly those with cerebral palsy, abnormalities in muscle tone are among the most common clinical symptoms. Damage occurring in various structures such as the thalamus, cerebral cortex, and basal ganglia can adversely affect muscle tone. Hypertonia is defined as an abnormal increase in resistance to externally imposed movement about a joint. It leads to limitations in activity participation, loss of motor control, and reduced quality of life. Hypertonia, which causes impairments in gross motor skills such as walking, stair climbing, and crawling, negatively affects the quality of life in childhood.

Muscle tone disorders in childhood can be classified into three main types: spasticity, dystonia, and rigidity. Spasticity is defined as a velocity-dependent increase in muscle tone associated with hyperexcitability of the tonic stretch reflex. Dystonia is a movement disorder characterized by sustained or intermittent involuntary muscle contractions that cause twisting, repetitive movements, abnormal postures, or a combination of these. Rigidity refers to bidirectional, velocity-independent resistance to passive movement, which may involve simultaneous co-contraction of agonist and antagonist muscles. In some cases, more than one type of tone abnormality may coexist.

Several assessment tools have been developed to evaluate different subtypes of hypertonia or general increases in tone. The most commonly used methods in clinical and research settings include the Modified Ashworth Scale (MAS), the Modified Tardieu Scale (MTS), and the Barry-Albright Dystonia Scale (BADS). While these scales evaluate different aspects of hypertonia, they do not distinguish between its subtypes. The Hypertonia Assessment Tool (HAT) was developed to address the need for a single instrument capable of differentiating among hypertonia subtypes. Introduced to the literature by Fehlings et al. in 2010, the HAT has been shown to be a valid and reliable tool for assessing the three subtypes of hypertonia in children with cerebral palsy.

The HAT involves observing an extremity joint during passive stretch and voluntary movement to detect increased tone or resistance. The scale consists of seven items-two assessing spasticity, two rigidity, and three dystonia. It can differentiate hypertonia subtypes in both upper and lower extremities and takes approximately five minutes to administer per limb. Studies in various patient populations have reported moderate to good levels of validity and reliability.

Translating psychometrically robust assessment tools into Turkish will expand the number of instruments available for clinical and research use in our native language. Therefore, the aim of this study was to translate the Hypertonia Assessment Tool into Turkish and to evaluate its validity and reliability in children with motor disorders.