Foot Drop in a Diabetic Patient

Author: V. Dimov, M.D., Cleveland Clinic
Reviewer: S. Randhawa, M.D.

72 yo CM woke up this morning with weakness in his left leg. He noted difficulty in lifting up his left foot from the floor. He has no other complaints.

The patient has bought a computer recently and has been browsing the web, sitting with legs crossed for prolonged periods.

PMH:
DM 2, HTN

Medications:
Lisinopril, Cardizem, Insulin 70/30

Physical examination:
VSS
WD/WN
Extremities: no c/c/e
5/5 RLE; 3/5 left foot dorsiflexion; sensation is intact

ORGN FN is a mnemonic for grading the muscle strength:

5 = OK
4 = Resists movement
3 = Gravity overcome
2 = No gravity overcome
1 = Flicker of movement
0 = No movement at all

What is the likely diagnosis?
Peroneal palsy or foot drop

The most likely reason is mechanical trauma to the peroneal nerve at the fibular head. The trauma is due to the body position of sitting for prolonged periods with crossed legs. Peroneal palsy is more common in diabetic patients because they may already have underlying subclinical ischemia which is exacerbated by the mechanical trauma.

What is the treatment?
Splint if the peroneal paralysis is complete. In this patient, the paralysis is incomplete and no specific treatment is needed. He should avoid sitting with legs crossed.

In no function is recovered in 3 months, a decompression surgery may be considered.

What are the chances for recovery after a peroneal palsy?
With partial nerve palsy, more than 80% of patients will recover completely.
With complete palsy, less than 40% of patients will have a complete recovery.

Final diagnosis:
Peroneal nerve palsy due to mechanical trauma (sitting with crossed legs)



Common peroneal nerve (click to enlarge the image). Image source: Gray's Anatomy, 1918 edition, public domain.

What is a "peroneal strike"?
"Peroneal strike" is a potentially disabling blow to the side of the leg, just above the knee. The attacker aims at the common peroneal nerve, a hand span above the knee, towards the back of the leg. The strike is made with baton or shin kick. The technique is a part of the pressure point control tactics used in martial arts or by law enforcement agents. The "peroneal strike" had gained a horrible notoriety as a torture technique used against prisoners of war.

References:
Peroneal Nerve - Wheeless' Textbook of Orthopaedics
Peroneal Mononeuropathy - eMedicine
Clinical and electrophysiological recovery from peroneal palsy - Acta Neurol Scand. 1986 Oct
Peripheral Neuropathy - Merck Manual
Mononeuropathy in Diabetes Mellitus - The University of Chicago
Classification of diabetic neuropathy - UpToDate (subscription required)

Related:
Peripheral Neuropathy. JAMA Patient Page, 03/2008.

Created: 09/20/2006
Updated: 03/04/2008

5 comments:

  1. why would the guy with one day history of footdrop due to cross leg position causing the peroneal nerve palsy require decompression surgery after 1month in case not resolved with the conservative surgery?

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  2. Other differentials for foot drop include: L5 radiculopathy (in which case foot invertors will also be weak, and commonly is associated with radicular back pain) or ALS (which will have other upper and lower motor neuron findings, commonly including bulbar dysfunction/dysphagia), although this case points fairly directly to a compressive peroneal mononeuropathy. If in doubt, an EMG about 3 weeks after onset of weakness can help tease out the precise diagnosis.

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  3. Yes, this is a case of pure peroneal palsy. His age, DM & HTN all contribute to this ischemia.

    Thanks for the note on peroneal strike, which is educational !

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  4. Why is this man on insulin when he have DM2?

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    Replies
    1. Probably bc his BG/A1C was not controlled by oral agents or he had contraindications to them!

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