Saturday, June 17, 2017

Differentiating peroneal neuropathy, sciatic nerve injury and L5 radiculopathy

This post is on differentiating weak dorsiflexion of foot - I made a little algorithm on it. (I'll add images later)

If there's weakness in foot dorsiflexion, check plantar flexion and inversion.

If plantar flexion and inversion is normal: Peroneal neuropathy.

If plantar flexion and inversion is weak: Check hip movements.

If weakness at hip joint: S5 radiculopathy.
If no weakness at hip joint: Sciatic nerve compression.

You can differentiate based on sensory levels and reflexes too but this is easier.

Conclusion:
Peroneal nerve supplies the dorsiflexors and evertors of the foot. There will be no weakness in plantar flexion and inversion in peroneal nerve injury.

Hip abduction is an action of Gluteus medius and minimus muscles. These are Superior gluteal nerve innervated muscles. This nerve arises from L4, L5 and S1 roots . If there is hip abduction deficit with foot drop, it means pathology at the radicular ( root) level. 


Here's the reading material.

Common peroneal neuropathy presentation:
- Acute foot drop (difficulty dorsiflexing the foot against resistance or gravity).
- Patients describe the foot as limp; there is a tendency to trip over it unless they compensate by flexing the hip higher when walking, producing what is called a "steppage" gait.
- Patients may also complain of paresthesias and/or sensory loss over the dorsum of the foot and lateral shin.
- Examination typically reveals weakness in foot dorsiflexion and foot eversion (deep and superficial peroneal nerve-innervated, respectively), with normal inversion and plantar flexion (posterior tibial nerve).
- Sensory disturbance is confined to the dorsum of the foot, including the web space between digits 1 and 2 and the lateral shin.
- Reflexes are normal.

Sciatic nerve injury presentation:
- Weakness affecting most of the lower leg musculature, including the hamstrings.
- Hip flexion, extension, abduction and adduction, and knee extension are normal.
- Sensory loss involves the entire peroneal, tibial, and sural territories.
- In the lower leg, however, the medial calf and arch of the foot may be spared secondary to innervation by the preserved saphenous nerve (a branch of the femoral nerve). Sensation is also spared above the knee both anteriorly and posteriorly.
- The knee jerk is normal, but the ankle jerk is unobtainable.

L5 radiculopathy presentation:
- Back pain that radiates down the lateral aspect of the leg into the foot.
- On examination, strength can be reduced in foot dorsiflexion, toe extension, foot inversion, and foot eversion.
- Mild weakness in leg abduction may also be evident in severe cases due to involvement of gluteus minimus and medius. Atrophy may be subtle; it is most readily observed in extensor digitorum brevis.
- Sensory loss is confined to the lateral shin and dorsum of the foot.
- Reflexes are generally normal.

That's all!
-IkaN

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