Motor Conditions

Muscular Dystrophy

This refers to a group of degenerative disorders which lead to skeletal muscle breakdown and weakness over time

– There are over 30 different disorders, but a few are much more common that the rest.

– Each has a different pattern on inheritance, which can be X-lined or autosomal.

General Diagnosis:

– Blood test shows raised creatinine kinase –> due to breakdown of skeletal muscle

– Genetic testing and muscle biopsy is diagnostic

General Management:

– No cure available

– Steroids slow muscle degeneration and anticonvulsants control seizures

– Aim to maximise quality of life with MDT approach

Duchenne muscular dystrophy

This is a type which is due to a X-linked recessive mutation in dystrophin

– The mutation is usually a serious nonsense or frameshift mutation

– Dystrophin connects the cytoskeleton of muscle fibres to the extracellular matrix through a protein complex in the cell membrane, stabilising the muscle cell membrane

– A lack of dystrophin results in reduced stability of muscle cells

– Over time, muscle cells become damaged, releasing creatinine kinase and Ca2+ enters, causing cell death

– This leads to muscular atrophy and replacement with fat and fibrotic tissue

Symptoms:

– Poor balance and progressive inability to walk

– Proximal progressive muscle weakness that occurs from around the ages of 4-5

– Gower’s sign –> using the arms to stand up from a squatting position

– Calf pseudohypertrophy

– Can have associated intellectual impairment

– Eventual death from cardiac/respiratory failure or dilated cardiomyopathy

Becker muscular dystrophy

This is very similar to Duchenne but is caused by a missense mutation in dystrophin

– This mutation means that one end of the protein dystrophin can anchor the cytoskeleton which means that the skeletal muscle is more stable than in Duchenne’s

– This is a less severe mutation and so give symptoms at a later age

Symptoms:

– Similar symptoms to Duchenne but symptoms start about 5 years later

– Less likely to have learning disabilities

Myotonic dystrophy

This is a dystrophy in which muscles contract but are unable to relax.

– It is an autosomal dominant condition due to a mutation in DMPK gene (type 1) or CNBP gene (type 2)

– In type 1, there is a trinucleotide expansion of GTG to over 50 repeats which lead to symptoms.

– Symptoms can appear from anytime from childhood to young adults

Symptoms:

– Worsening muscle loss and weakness –> muscles contract but inability to relax them

– Associated neurological symptoms –> Intellectual disability and cataracts

Cerebral palsy (CP)

This is a group of permanent motor disorders that appear early in childhood due to a damage of the developing motor neural pathways in the central nervous system.

– Whilst it is primarily a motor disorder, it is often accompanied by other symptoms to to damage to other neurological structures

Causes:

– Maternal infection –> associated with CMV and rubella

– Foetal infection –> neonatal meningitis

– Birth ischaemia –> asphyxia during birth, trauma

It is classified depending on the nature of the motor disorder:

Symptoms:

This gives general features + signs of the specific type of cerebral palsy:

– Delayed motor milestones –> children learn to roll over, sit, crawl and walk at a later age

– Problems with walking –> can display spastic gait, ataxic gait

– Persistence of the primitive reflexes

– May have associated learning difficulties, seizures, neurological problems (deafness)

Diagnosis:

– Clinical diagnosis based on history and physical examination. Can use MRI to establish cause

Management:

– Needs an MDT approach

– Aim is to help physical problems to maximise the patient’s independence with occupational therapy, physiotherapy, speech therapy

– If seizures –> use anticonvulsants

– For spasticity –> benzodiazepines (e.g., baclofen)