Muscular dystrophy, types, pathophysiology, symptoms, investigation, physiotherapy management

 Muscular dystrophy is a group of rare hereditary progressive disease in which muscle fibers are usually susceptible to damage. 

Muscular dystrophies are genetically determined myopathies in which progressive degeneration & wasting of muscles occur. 

Dystrophies can be of 3 types 

1. Congenital muscular dystrophy
2. Genetic muscular dystrophy
3. Metabolic muscular dystrophy

Epidemiology:- Commonly seen in males. 

Pathophysiology:-

• Deficiency of dystrophin protein (due to defect in the XP21 gene which codes dystrophin) 
• Loss of properties of skeletal muscle cells membrane ( Dystrophin is essential to maintain the properties of skeletal muscle cells membrane) 
• Cell break down
• Release of all contents of cell into the serum
• Death of cell i.e necrosis of muscle cells
• Fatigue, weak & dystrophin muscles
• Elevated serum creatinine phosphokinase levels. 

Classification:- based on inheritance & clinical picture

X-linked recessive - Duchenne muscular dystrophy, Becker Muscular dystrophy. 

Autosomal dominant - Fascio scapular humeral Muscular dystrophy

Autosomal recessive - Limb girdle Muscular dystrophy. 

Duchenne Muscular dystrophy:-

This is the most commonest form of Muscular dystrophy. This disorder is of X-linked recessive type of inheritance. 50% of females are carriers 50% of males are affected. 

Mutation rate is higher than in any other X-linked hereditary disease. This accounts for about 50% of the sporadic cases. 

Incidence:- 1 in 3500 male births. 

Clinical features:-

• Delayed early motor development usually noted between ages 1& 3 years, followed by scoliosis, contractures & eventually loss of ambulation at around 12 years of age. 
• Pseudohypertrophy of calf is a characteristic features occuring in about 80% of the patients this may lead to contracture of the calf muscle
• Increased lumbar Lordosis Anterior pelvic tilt
• Shortening of hip flexors & lengthening of hip extensors. 
• Thoracic scoliosis, protruded head, Rib hump
• Cardiomegaly, arrhythmias
• Ventilation is affected pattern becomes poor. 
• Sometimes laryngeal & pharyngeal muscles are affected which may lead to aspiration pneumonia. 
• Proximal muscles are more affected than distal if glutei/quads are involved, it leads to Waddling gait. Axial muscles are involved, it results in Sway back posture, lower limbs are more involved than upper limbs. 
• Gowers sign is seen indicates pelvic muscle weakness
• Muscle imbalance is the commonest features
• IQ of child is 15-20% less than the normal child
• Symptoms appear by 3years, becomes apparent by 6years, Ambulance is lost by 11years, patient sticks to wheelchair by 15years, patient dies by age of 20years.

Investigation:- 

Electromyography(EMG) - to rule out pathological action potential

Serum test:- to find out elevated CPK levels

Muscle biopsy - to show typical findings. 

Treatment 

Prednisolone 0.15 mg/day slows the progression of disease upto 3years.

Life expectancy has raisen upto 30years with the use of surgery to correct scoliosis, active control of contractures & non- invasive ventilation. 

Most of the treatment is symptomatic. 

Beckers Muscular dystrophy:-

It is rare than DMD cardiac muscles are spared

 incidence - 1:35000 

Facio Scapular humeral muscular dystrophy:- it is an autosomal dominant disorder

Incidence:- 1-2 : 100000

Mechanism by which the mutation causes disease is unknown

Clinical features:- facial weakness, peri scapular weakness producing winging of scapula 

Weakness of humeral muscle

Proximal lower limb pattern of weakness giving a camel backed gait. 

Examination:-

 Vital signs - pulse rate, bp, respiratory rate, temperature. 

Consciousness - GCS 

Gait - lordotic stance, wadding gait. 

Bowel & bladder - rarely involved. 

Physiotherapy Management:-

1. Counseling should be done
2. Chest care :- Breathing exercises, postural drainage & percussion of chest & assisted coughing need to be taught to patient to clear the chest secretions
3. Clothing:- need to be loose, light & warm, plastazote boots covered with leather solves problem in equinovarus feet. 
4. Postural correction:- spine must be under review Scoliosis may occur, light weight thoraco- lumbar sacral orthotics is worn,  scoliosis may be treated surgically by luque procedure. 
5. Lifting:- showing how to roll into bed & use of sliding boards 
6. Exercises:- PNF technique more beneficial, strengthening exercises not allowed, active ROM exercises should be encouraged, 
7. Strengthening &splinting :- parents need to taught how to stretch hips, knees, & foot later shoulder, elbows & wrist stretched, splints - POP night split or AFO for day, night
8. Recreation:- suitable activities fishing, tv games, photography etc can be encouraged. 
9. Family education plays important role
10. Prolongation of ambulation:- walking should be encouraged for as long as possible
11. Surgery &orthotics:- percutaneous tenotomy. 
12. Gait :- child must learn to balance & walk in a lordotic position without using sticks or Walker, standing chair is also beneficial in preventing contractures
13. Wheelchair :- as walking is difficult, with or without orthosis wheelchair is useful.