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Myotonic Muscular Dystrophy

In this not only striated muscle severely affected but smooth muscle of the alimentary tract and uterus is also involved, cardiac function is altered and patient have multiple and variable endocrinopathies, immunologic deficiencies, cataracts, dysmorphic facies, intellectual impairment.

 

Other characteristic features:

  1. Myotonia
  2. Distal distribution of muscle weakness and wasting myalgia do not occur
  3. Exhibits a pattern of anticipationQ in which each successive generation has a tendency to be more severely involved than previous generation. 

VII. Spinal Muscular Atrophies

 

 

A. ​Spinal Muscular Atrophies

 

Spinal Muscular Atrophies (SMA) are degenerative disease of motor neurons that begin in fetal life and continue to be progressive in Infancy and childhood.


Three Types

  1. Severe infantile form Werdnig Hoffmann disease Type-I
  2. Late Infantile form Type-II
  3. Chronic or juvenile form Kugelberg – Welander disease Type-III 

Clinical Manifestations

 

Type – 1

  1. Loss of fetal movement in later part of pregnancy and polyhydroamniosQ
  2. Severe hypotoniaQ
     
    Generalized weakness
     
    Thin muscle mass
     
    DTR absentQ
     
    Involvement of tongue, face and jaw muscle and sparing of extra ocular muscle and sphinctersQ
  3. Having respiratory distress and unable to feed. Death occurs with in 2 year. 

Type – 3 Kagelberg Welander disease

  1. May appear normal in infancy
  2. The progressive weakness is proximal in distribution
  3. Fasciculation are specific clinical sign of denervation of muscle. Q
  4. Myalgia are not a feature of SMAQ
  5. Heart is not involved and intelligence is normalQ 

Table: Inflammatory myopathies
 

Idiopathic

  1. Juvenile dermatomyositis
  2. Polymyositis
  3. Inclusion body myositis
  4. Myositis as overlap syndrome
  5. Others:
    1. eosinophilic myositis
    2. Focal nodular myositis
    3. Sarcoid myopathy

Infectious

  1. Viral myositis:
    1. Influenza
    2. human immunodeficiency virus
    3. others
  2. Parasitic myositis
    1. trichinosis
    2. toxoplasmosis
    3. cysticercosis
  3. Bacterial myositis
  4. Fungal myositis 

Table: Causes of floppy infant syndrome


Central nervous system

 

Perinatal asphyxia, neonatal encephalopathy, kernicterus, cerebral palsy (atonic type), intracranial hemorrhage, chromosomal anomalies including Down syndrome, inborn errors of metabolism (aminoaciduria, mucopolysaccharidosis, cerebral lipidosis)


Spinal cord

 

Anterior horn cell disease: Werdnig Hoffman (spinal muscular atrophy), poliomyelitis


Peripheral nerves

 

Familial dysautonomia, hereditary motor sensory neuropathy


Myoneural junction

 

Neonatal myasthenia gravis, infantile botulism, following antibiotic therapy


Muscles

 

Muscular dystrophies, congenital myotonic dystrophies, congenital myopathies (central core disease, nemaline myopathy), polymyositis, glycogen storage disease, arthrogryphosis multiplex congenita


Miscellaneous

 

Protein energy malnutrition, hypothyroidism, rickets, Prader¬Willi syndrome, Ehler-Danlos syndrome, cutis laxa

 

Differentiating features of a floppy infant according to site of involvement

 

Extent of weakness

 

 

 

 

Site of involvement

Face

Arms

Legs

Proximal vs distal weakness

Deep tendon reflexes

EMG

Muscle biopsy

Central

-

+

+

>or=

Normal or increased

Normal

Normal

Anterior horn cell

±

++++

++++

>or=

Absent

Denervation potentials, Fasciculations

Neurogenic atrophy

Peripheral nerve

-

++

+++

< 

Decreased / absent

Abnormal NCS, Denervation potentials

Denervation pattern

Neuromuscular junction

+++

++

++

=

Normal

Decremental response on repetitive stimulation

Normal

Muscle

Variable

++

+++

> 

Decreased

Short duration, polyphasic potentials

Characteristic

EMG electromyography; NCS nerve conduction studies





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