Hypotonia

Low muscle tone is a common finding. Remember the following points

Causes of Hypotonia

In new-borns

1. Anterior Horn cell disorders like Hypoxic-ischaemic myelopathy, Spinal muscular atrophy
2. Congenital myelopathy like Charcot Marie Tooth disease
3. Neuromuscular junction disorders like Congenital myasthenia
4. Congenital myopathy like Nemaline myopathy
5. Muscular dystrophy
6. Syndromes- like Downs syndrome, Prader Willi syndrome, Hypothyroidism, Tay Sachs disease, Marfans disease

In older children along with the above

• Multiple sclerosis
• Cerebral palsy
• Post meningitis, encephalitis

Examination of Hypotonia

History

Feeding difficulty at birth

Delay in gross development, like delayed walking

Inspection

The attitude of the patient in the bed

• The position of the child tells you about the tone.
• Like frog-like position in infants.
• Look for the degree of abduction at the shoulders and hip. The more hypotonic the child, the more the limb lies on the bed

Classical method

• Standing on the right side of the patient’s bed, ask the child to relax while lying supine.
• You need to assess the passive movements at each joint – the ankle, knee, hip and similarly on the upper limb t the wrist, elbow, shoulder
• Keep your left hand proximal to the joint where the muscle mass is maximum. For example- Keep your hand on the calf muscle when assessing the ankle joint
• Make the whole range of movement and assess the tone. If floppy you may shake the limb to make it obvious.

Palpation

• The muscles may be soft and flaccid to touch