BY

BHAVYA SHARMA

The term neuromuscular

disease defines disorders of

the motor unit and excludes

influences on muscular

function from the brain, such

as spasticity.

The motor unit has 4 components:

Motor neuron in the brainstem or anterior horn of

the spinal cord;

Axon(with other axons forming the peripheral

nerve);

Neuromuscular junction disorder; and

Myopathies (all muscle fibers innervated by a

single motor neuron).

The motor unit is influenced by suprasegmental or

upper motor neuron.

Muscular Dystrophies

Congenital and Metabolic Myopathies

Anterior Horn Cell Disorders

Neuromuscular Junction Diseases

Weakness, poor cough, retained airway

secretions

Inability to lift extremities against gravity

Muscle wasting

Low muscle tone (hypotonia)

Poor feeding, swallowing dysfunction

Failure to thrive

Increased respiratory rate

Use of accessory muscles of respiration

Recurrent infections

Night sweats

Weakness results either from -:

Upper motor neuron lesion e.g cerebral palsy causing increased tone,

brisk reflexes and extensor plantar response.

Lower motor neuron lesion causing hypotonia, depressed reflexes and

flexor plantar response.

Tone and strength should not be confused: Passive tone is range of

motion around a joint; Active tone is physiologic resistance to

movement.

Involvement of the face, tongue, palate, and extraocular muscles provides

an important distinction in the differential diagnosis.

Prenatal history

Acute flaccid paralysis

It’s a common sign of neuromuscular disorders.

CAUSES OF HYPOTONIA

Central Hypotonia-chromosome disorders, static insult, infections

(hyperactive reflexes)

Peripheral Hypotonia (distal weakness and wasting)

Neuromuscular junction (Myasthenia Gravis leads to fluctuating

wekness)

Muscular dystrophies(proximal weakness)

Anterior horn cells- spinal muscular atrophy (asso. with wasting,

hyporeflexes)

Neurometabolic condition- deficiencies

Serum Enzymes- creatine kinase

MM for skeletal muscle

MB for cardiac muscle

BB for brain

Mainly elevated in Duchenne muscular dystrophy.

Molecular Genetic Markers

Nerve Conduction Velocity

Electromyography- insertion of needle into belly of muscle → recording electric potentials in various states of contraction.

Imaging of Muscle

Muscle Biopsy- most important (vastus lateralis is sampled)

ECG

Classification-

Infectious - poliomyelitis

Motor neuron disease - amyotrophic lateral

sclerosis

Spinal muscular atrophy (SMA)

Autosomal Recessive disease

Type 1(Werdnig-hoffmann disease) present with profound hypotonia

and areflexia, respiratory weakness, poor swallowing and tongue

fasciculation. Children never learn to sit and Aspiration pneumonia

cause of death.

Type 2(Dubowitz disease) onset at 6-18 months and usually able to sit

unaided but may develop kyphoscoliosis, tremors.

Type 3(Kugelberg-Welander disease) onset >18 months and usually

able to walk

Treatment is supportive and respiratory care, management of feeding

and swallowing and provide adequate nutrition.

Guillain-Barrẽ syndrome is the most common.

Clinical patterns to a demyelating process include-

Presence of global areflexia

Moderate to severe muscle weakness with bulk

Motor symptoms

Hypertrophy of nerves

Guillain- Barrẽ Syndrome

Common cause of AFP

Immune mediated, rapidly progressive, predominantly motor, symmetric polyradiculoneuropathy

Condition can occur at any age within six weeks prior to symptom

Clinically the respiratory illness and weakness(2-

4weeks after onset) along with tachycardia, arrhythmia,

bladder dysfunction, labile blood pressure and

impaired thermoregulation.

Diagnosis

TREATMENT

IVIG at 2g/kg over 2-5 days or plasma exchanges if

child presents within 2-4weeks.

Donot respond give second course

General supportive care

Cardiorespiratory care and nutritional management.

MYASTHENIA GRAVIS

Autoimmune and autosomal recessive trait disorder

characterized by rapid fatigability of striated muscle.

Three clinical varieties-

Juvenile in late infancy and childhood showing extraocular

muscle weakness.

Congenital

Transient neonatal-symptoms arises after birth till 3rd day.

Occasionally associated with hypothyroidism, systemic

lupus erythematosus.

Acetylcholine receptor antibodies may be positive.

Electromyography show increases jitter or blocking.

Diagnostic test done by Edrophonium chloride(0.1-0.2mg/kg IV) and effects of weakness as distance b/w upper and lower lid is seen in 10sec.

TREATMENT

Mild myasthenia gravis require no treatment.

Cholinesterase inhibiting drugs such as

Neostigmine methylsulfate (0.4mg/kg) I/M every 4-6hr or oral neostigmine bromide.

Pyridostigmine (1-7mg/kg/day) in 4 divided doses

Prednisone(0.5mg/kg/day)

Thymectomy, Plasmapheresis, IVIG is effective in high circulating levels of anti-A ch receptor antibodies.

A group of genetically

determined, progressive primary

myopathy characterized by

degeneration and death of

muscle fibres, occurring at some

stage of the disorder.

–Duchenne muscular dystrophy

–Becker muscular dystrophy

–Myotonic muscular dystrophy

–Congenital muscular dystrophy

- Glycogenoses

- Mitochondrial

–Distal muscular dystrophy

–Others- Polymyositis

Dermatomyositis

inclusion body myositis

X-linked recessive

Absence of dystrophin protein

Slow to reach motor milestones

Symptoms appear in 2nd year, with clumsy walking or falling on walking or running on an uneven ground.

Muscles replaced by fat may appear hypertrophic

Child is mentally retarded

Life expectancy < 20 years with death related to respiratory failure or cardiomyopathy.

Gower Sign : Evident by 6 years of age-child trying to get up from squatting position, turns to side, lifts his trunk by supporting his weight on his arms and then stands up supporting the body with his hands.

Peudohypertrophy

of Calf Muscles in

Duchenne

Muscular

Dystrophy

Serum CPK elevated upto 15,000-20,000 U/L (normal

2000U/L)

EMG rarely necessary but useful in doubtful cases.

Histopathology of muscle show diffuse changes of

degeneration & regeneration.

Advanced genetic studies can find gene deletion.

Physiotherapy, exercises including walking & cycling

useful; tenotomy may be required for contractures.

Prednisone (0.75mg/kg/day) for 10days of each month to

avoid chronic complications.

Nemaline myopathy

Myotubular/Centronuclear myopathy

Central core disease

Multiminicore disease

Congenital fiber-type disproportion

myopathy

Genetics Autosomal recessive and dominant forms

First discovered in 1956 by Dr. Reyes

1/50,000 births

6 different mutations identified

Onset Infancy and early childhood

Clinical presentation Face, neck and proximal muscle

weakness

Absent deep tendon reflexes (DTR), normal creatinine

kinase

A form of centronuclear myopathy

Genetics X-linked recessive

Autosomal recessive and dominant

Onset Birth for X-linked recessive

Infancy and childhood for autosomal recessive

Adult for autosomal dominant

X-linked is most common form and most severe

Clinical Hypotonia, respiratory pump failure,

scaphocephaly