Introduction 

Batten Disease or Neuronal ceroid lipofuscinosis (NCL), is a group of rare neurodegenerative disorders. Varying in onset ages, it primarily begins in childhood, leading to a range of functional decline, including progressive vision loss and dementia. With gradual motor deterioration as a hallmark, loss of muscle strength and control could eventually progress into complete loss of voluntary movement. By providing a clearer understanding of the overall motor decline among Batten disease, heightened awareness and better management can be facilitated among caregivers and healthcare professionals to enhance the quality of life among those affected.^1,2

Understanding batten disease 

Batten disease is a group of inherited metabolic lysosomal storage disease (LSD), primarily 

caused by genetic mutations that impair the normal enzymatic intracellular debris clearance ability of lysosomes. Toxic endo-lysosomal storage is facilitated and accumulated among neurons in the brain, resulting in neuronal malnutrition and eventual loss, hence leading to progressive motor and cognitive decline.^1,3

There are currently 13 identified subtypes of Batten disease, each with a specific genetic mutation associated, defined as CLN (ceroid lipofuscinosis, neuronal) 1 to 13. The most common forms include congenital, infantile, late infantile, and, very rarely, adult-onset. While all subtypes vary with age-onset, affected brain areas, symptoms, and disease progression, they all share very similar symptoms. Despite the normal life expectancy among adult-onset subtypes, all others are, unfortunately, fatal.^1,3

Batten disease is progressive, so motor functions only worsen over time. While individuals usually exhibit mild clumsiness and weaknesses at the initial stages, these difficulties become more pronounced as the disease progresses, eventually causing complete paralysis, or even a vegetative state, associated with cognitive deterioration.¹

Motor regression, decline and its underlying mechanism 

While age onset and rate vary, motor decline has been a universal hallmark of Batten disease.¹ It normally shows up between the age of 2 to 7, or later during adolescence or adulthood.³

Loss of acquired motor skills is usually one of the first functional declines occurring in Batten disease.³ Affected babies and children usually meet some motor milestones, such as crawling, walking, and self-feeding, with a period of normal growth and development at first. Subtle declines such as becoming increasingly clumsy, as well as challenges in performing precise movements and manipulating objects, arise at an early stage of disease but are often mistakenly considered normal developmental variations.¹ Yet, as the disease advances, these signs become more evident, leading to a cease of motor development and rapid loss of previously acquired motor abilities.¹ 

The progressive neuronal degeneration occurs in various brain regions, such as the cerebral and cerebellar cortices, and the subcortical grey nuclei, where swollen cerebral neurons have been discovered.³ The widespread neuronal loss due to the degeneration of crucial regions for motor control, coordination, and movement planning, will disrupt the normal motor circuits functioning.³ Hence, inducing the board-ranging motor impairments and decline, including weakness, stiffness, spasticity, and ataxia in Batten disease.³

With muscle weakness as a primary manifestation, leading to strength decline, the possible later onset of extrapyramidal symptoms such as tremors, tics, spasms, dystonia and myoclonus, could also significantly impair coordination, balance, and movement control as the disease progresses, leading to overall mobility deterioration.¹ 

Muscle weakness, stiffness, and spasticity 

Muscle weakness is prominent in Batten disease. In fact, due to the progressive degeneration of the motor cortex and impairment of cortico-descending connectivity, both voluntary and involuntary muscles affecting the limbs, eyes, and swallowing abilities are weakened.³ Simple actions like walking, lifting or staring at objects, even speaking and swallowing are increasingly challenging due to reduced muscle strength and force generation.³ As the disease progresses, all voluntary movements and posture control are lost, and individuals become wheelchair- and bed-bound, completely relying on caregivers.^1,3 

Stiffness (hypertonia) is also common among Batten disease. Characterized by increased muscle tone and resistance to movement, stiff muscles make it difficult to initiate and control movement, limiting one’s range of motion and flexibility. As this potentially affects various muscle groups, it causes significant functional limitations and discomfort in affected patients.^1,3 

Spasticity, characterized by involuntary muscle contractions all at once, is also prevalent among Batten disease patients. This can cause muscle tightness, rigidity, hypertonia, jerky movements, and even contractures and deformities in the long run, further hindering voluntary movements and motor coordination, and heightening challenges in performing precise fine motor tasks.⁴ 

Gait abnormalities and mobility issues 

Gait abnormalities are deviations from normal gait patterns. In Batten disease, gait abnormalities manifest differently among subtypes. While gait can show up as uncoordinated and non-rhythmic among the CLN1 subtype, it is clumsy, ataxic and spastic among those with CLN2, and Parkinson-like for those with CLN3.⁵ As the disease advances, gait abnormalities become more prominent, leading to progressive ambulation loss, more reliance on mobility aids, and ending up wheelchair- and even bed-bound.³ 

Beyond gait abnormalities, mobility challenges are also affected by muscle weakness, stiffness, and spasticity among Batten disease patients, which can impair walking abilities, resulting in frequent falls and balance problems. 

Slowed walking and endurance reduction are also common in Batten disease, leading to overall mobility deterioration. Patients may require environmental modifications for support in their daily activities, such as those requiring physical strength, balance, and coordination. These activities could become increasingly difficult over time, eventually leading to patients losing motor autonomy and completely depending on their caregivers.³ 

Challenges with fine motor skills 

Ataxia (challenges with fine motor skills) is another significant symptom of Batten disease. Fine motor skills involve the coordination of the small muscles in one’s hands and fingers, allowing for precise movements and activities. Ataxia is mainly manifested in the Batten disease clinical subtypes CLN 1, 2, 6, 7 and 8,variants³. Due to the degeneration of Purkinje cells and deep cerebellar nuclei, as well as spinocerebellar involvement, individuals with Batten disease often experience manual dexterity and coordination difficulties as the disease progresses. This makes tasks requiring intricate finger movements, such as grasping, and managing small objects and self-care tasks like buttoning clothes, increasingly difficult, leading to reduced independence.³ 

Hand-eye coordination is also affected by Batten disease. This is often associated with strabismus and progressive visual loss; therefore, individuals might have difficulties in performing tasks requiring simultaneous visual tracking and precise manual movements.^1,3 Activities like drawing, writing, or playing instruments become progressively more challenging as the disease advances. 

Loss of fine motor control may also affect self-care activities, such as grooming, dressing, and feeding. Basic tasks like buttoning clothes, using zippers, or personal hygiene handling also become more effortful, and eventually might become impossible without a caregiver’s assistance.  

Evaluation and management of motor decline 

A comprehensive and multidisciplinary approach is required in evaluating and managing motor deterioration among individuals with Batten disease. Regular assessments by a team of healthcare professionals encompassing neurologists, geneticists, and rehabilitation specialists are essential for disease progress monitoring and tailoring interventions for the affected population accordingly.  

Physical and occupational therapy interventions

Physical therapy is crucial in managing motor decline. Working closely with Batten disease individuals, physical therapists can develop customized stretching and strengthening exercise programs to help maintain muscle strength, improve balance, and maximize the functional abilities of patients. 

Occupational therapy is also vital in handling motor decline. Occupational therapists assess and address difficulties in activities of daily living, such as self-care, fine motor skills, and functional mobility. They also provide energy conservation techniques, assistive devices, and adaptive techniques to enhance independence and quality of life among patients.¹

Assistive devices and adaptations 

Assistive mobility devices and adaptations are crucial in providing support and enhancing independence among patients with Batten disease. Mobility aids such as walkers, wheelchairs, orthotic devices like AFOs, and adaptive postural and seating systems may enhance support and independence among individuals. Modifications to home environments, such as grab bars, ramps, and even hoist lifting installation, can improve accessibility and safety for both the individual and caregivers.¹  

Medications for symptom management 

There is currently only one FDA-approved medication for Batten disease, cerliponase alfa, which is limited to a specific population - children with the CLN2 subtype. In other circumstances, medications for the management of symptoms, such as muscle relaxants, can still be prescribed to manage muscle stiffness, seizures, muscle spasms, and myoclonus to improve mobility and comfort.¹

Regular follow-ups and reassessment are crucial to adjust treatment plans and address emerging challenges as the disease progresses, optimizing functional ability and enhancing quality of life. 

Prognosis, impact on quality of life and daily functioning 

Batten disease is generally fatal (except for one adult subtype that does not shorten life span), with a significant impact on quality of life and daily functioning.¹ As the disease progresses, with severe neurological deterioration, individuals eventually become blind, with a complete loss of motor and cognitive functions, unable to walk, communicate, or sit independently.¹ With these profound functional inabilities, daily activities become increasingly challenging, affecting social interactions, educational opportunities, and overall well-being, incurring a loss of motor autonomy and complete reliance on caregivers.³

Emotional and psychological support 

Emotional and psychological support is essential for Batten disease patients undergoing motor decline. The progressive nature of the disease and the challenges of limited mobility can lead to emotional distress and psychological struggles. Therefore, access to counselling groups and resources for coping strategies can provide individuals and their families with much-needed emotional support. By focusing on the patient's emotional well-being, alongside their physical care, these interventions can help address feelings of frustration, anxiety, depression and social isolation. This will benefit individuals and their families to receive comprehensive support and to navigate through the challenges of motor decline, whilst enhancing overall quality of life. 

Summary 

The motor decline is a prominent feature of Batten disease, a rare neurodegenerative disorder.  Individuals usually experience motor skills regression, progressive muscle weakness, stiffness, spasticity, gait abnormalities and ataxia, which significantly impact their mobility, and coordination, causing gradual loss of motor autonomy and total reliance on caregivers. While regular assessments from multidisciplinary healthcare professionals are vital to monitor disease progression, physical and occupational therapy interventions, assistive device adaptations and symptomatic medications are also important in managing motor decline. Despite the undeniable challenges induced, a comprehensive healthcare approach is essential to address the physical, emotional and psychological needs of the affected population. Ongoing research is also bringing hope and an optimistic future in halting or slowing down the disease progression, in enhancing the quality of life for the patients and their loved ones.