Equinovarus Spasticity (Footdrop) in MS

Footdrop
High-Stepping Gait

Foot drop, or drop foot, is an abnormal neuromuscular disorder that affects a patients ability to raise their foot at the ankle. It is further characterised by the inability to point the toes toward the body, or move the foot inward or outward.

Walking becomes a problem as the patient has a tendency to drag the foot which may cause tripping or stumbling. The patient may also develop a high-stepping walk called a Steppage Gait or Footdrop Gait.

Equinovarus spasticity is usually associated with damage to the peroneal nerve, although in MS it is more likely to be due to demyelination of the sciatic nerve. The sciatic nerve splits, in the thigh, into the posterior tibial nerve and the peroneal nerve.

Possible Causes

  • Compressed nerve root, usually in the lower spine, due to a ruptured lumbar disk
  • Pressure or injury to the peroneal nerve in the lower leg, such as from sitting with legs crossed for long periods
  • Peripheral nerve disorder (neuropathy)
  • Motor neuron disease, such as amyotrophic lateral sclerosis (ALS)
  • Muscle disorders (myopathies)
  • Tumour or stroke affecting areas of the brain that control movement of the legs
  • Disorders of the spinal cord such as tumours or multiple sclerosis

Treatments

Patients may be fitted with an Ankle Foot Orthosis (AFO), a brace, usually plastic, worn on the lower leg and foot to support the ankle.

Functional Electrical Stimulation is a method that can be used to help footdrop in MS by lifting the foot during the swing phase of gait to avoid the toes catching on the floor leading to possible falls. Electrical signals are applied artificially to the appropriate weak muscle and this causes the foot to lift and this counteracts the weakness. This may be fitted to the leg externally or it may be surgically implanted.

Physiotherapy may be employed to incorporate gait training.

References:

Ankle Foot Orthosis Definition 
Spine Universe

Footdrop in Multiple Sclerosis – Equinovarus Spasticity
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