Spinal muscular atrophy

1. MUZAMMIL HAMEED
NEUROPHYSIOLOGY
SPINAL MUSCULAR ATROPHY(SMA)
 Spinal muscular atrophy (SMA) is a neuromuscular disease
characterized by degeneration of lower motor neuron in the spinal
cord, resulting in progressive proximal muscle weakness and paralysis.
CAUSES OF SMA
 SMA is caused by defects in the Survival Motor Neuron 1 (SMN1)
on chromosome 5 gene that produce the SMN protein.
 The SMN protein is critical to the health and survival of the nerve
cells in the spinal cord responsible for muscle contraction (motor
neurons).
ONSET ON SMA
 The disease generally manifests early in life and is the leading genetic
cause of death in infants and toddlers.

2. CLASSIFICATAION
 SMA is classified according to the age at which symptoms develop and
how severe they are
SMA TYPE -1 (Werdnig-Hoffmann disease)
 Most severe type and most common
 Onset: less then 6 months of age
CLINICALLY:
1) Proximal weakness
2) Lower limbs weaker then upper limb
3) The babies have their limbs floppy (hypotonia). They
are usually unable to raise their head (no head control)
and sit without support.
4) Trouble breathing, feeding, and swallowing.
SMA TYPE - 2 (intermediate)
 Less severe then type - 1
 Onset :7-18 months of age
CLINICALLY:
1) Can sit without any support
2) Can achieve standing position
3) Can not walk without any support
4) Kyphoscoliosis

3. SMA TYPE - 3 (mild, Kugelberg-Welander disease)
in adulthood
 Mildest form of SMA
 Onset : > 18 months age
CLINICALLY:
1) Can walk independently
2) Patient need wheelchair
3) Walking or getting up from a sitting position difficult.
4) They may also have balance problems, an abnormal way
of walking, difficulty running or climbing steps, a slight tremor of their
fingers.
SMA TYPE - 4(Adult-onset)
1)Type IV SMA is a less common form that begins in adulthood.
2) The symptoms are usually mild to moderate.
3) Symptoms include muscle weakness in the hands and feet, difficulty
walking, muscle tremor and twitching.
4) Type IV SMA doesn't affect life expectancy.
CLINICAL FEATURES OF SMA PATIENT:
 weakness is usually symmetrical and more proximal than distal;
generally it is greater in the legs than in the arms.
 impaired head control, weak cry and cough, swallowing

4. DIAGNOSIS OF SMA
 NCS shows reduced motor amplitude and normal sensory responses
 EMG shows Neuropathic response high amplitude long duration
polyphasic waves
FLOPPY BABY (HYPOTONIA)