200 Section - Adult-onset great toe Focal dystonia or Hallux Saltans due tenosynovitis at Knot of Henry. A case report

Adult onset focal dystonia of great toe.

Case Description:

A 67 year old male presented with complaints of flexion left great toe on walking with tingling and numbness of toes for 2 years.   Patient had undergone surgery at 2^nd webspace Morton’s neuroma. Pain was 0/10 and increased to 9/10.  The flexion of great toe coincided with before heel strike with spontaneous release. There was no tenderness.

There was no sensory deficit. MRI showed flexor hallucis longus (FHL) tenosynovitis at knot of Henry, suspected small Morton's neuroma at the 3rd webspace. Ultrasound revealed  muscle fasciculation of the foot muscles and soleus. Laboratory investigations were within normal limits.

Nerve conduction studies/EMG revealed bilateral medial and lateral plantar sensorimotor neuropathy; mild bilateral peroneal motor neuropathy; chronic bilateral L5-S1 radiculopathy.

The patient underwent two injections at the FHL sheath at the plantar aspect of the foot. The distance of walking increased up to four miles. Flexion of great toe could be voluntary controlled.

Discussions:

Hallux Saltans (triggering of great toe) and focal dystonia of great toe are rare. Hallux Saltans has been noted in Ballet dancers due to flexor hallucis longus tenosynovitis at the ankle. Focal dystonia for has rarely been mentioned. Various treatments have been mentioned including conservative treatment, Botulinum toxin injection and surgery. This patient was treated steroid injection in the flexor hallucis longus sheath under ultrasound guidance.

Conclusions:

This is a rare presentation of focal dystonia of flexor hallucis longus associated with flexor hallucis longus tenosynovitis at the knot of Henry, in association other EMG findings which benefitted from a steroid and lidocaine injection.