Translating batteries with good psychometric properties into Turkish will increase the number of assessment batteries we can use in our language for clinical and academic studies. Therefore, the aim of our study was to verify the validity, reliability, and translation into Turkish of the Hypertonus Assessment Tool for 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.

Inclusion Criteria:

• as voluntary participation in the study,
• a diagnosis of a neuromotor disorder under the age of 18,
• sufficient cognitive ability to follow verbal commands

Exclusion Criteria:

• Patients with any other systemic disease,
• Who had received botulinum toxin A injections or undergone surgery within the past three months,
• Be unable to follow verbal instructions
• Medical treatment had been modified within the last month

This methodological study was designed as a Turkish language adaptation, validity, and reliability study. It will be conducted at the Developmental Physiotherapy and Pediatric Rehabilitation Unit of the Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Gazi University, between January 15, 2025, and January 15, 2026. Children with neuromotor disorders diagnosed by a pediatric neurologist and attending routine clinical follow-up visits will be recruited through convenience sampling. The total sample size was determined as 70 participants, corresponding to ten times the number of items in the scale. Children whose parents provide written and verbal informed consent will be included in the study.

All IPD collected throughout the trial, only IPD used in the results publication.