Peripheral Nerve Hydrodissection

What is nerve entrapment?

Nerve entrapment is when a sensory (touch) or motor (muscle) nerve or mixed (both touch and motor) nerve gets pinched (entrapped) causing symptoms, such as numbness or weakness or a combination of both.

What are some of the common sites for peripheral nerve entrapment?

Common sites of peripheral nerve entrapment include but are not limited to:

Brachial plexus (Thoracic outlet syndrome)

  • At the Anterior or middle scalene
  • At the pectoralis minor

Median nerve

Radial nerve

  • At the arm (radial tunnel syndrome)
  • At the elbow (Supinator syndrome)
  • At the back of hand/ dorsal wrist (possibly from a wrist cyst (ganglion)

Ulnar nerve

  • At the elbow (Cubital tunnel syndrome)
  • At the wrist (dorsal ulnar cutaneous nerve syndrome)
  • At the hand (Hook of hamate syndrome)

Sciatic nerve

  • At the pelvic outlet (piriformis syndrome)
  • At the posterior hip (ischio-femoral space syndrome)

Femoral nerve

  • At the anterior hip
  • At the medial thigh (Adductor canal syndrome)

Lateral femoral cutaneous nerve:

  • At the level of the hip (Meralgia paresthetica)

Saphenous nerve

  • At the medial thigh/knee (often from trauma)
  • At the lower leg (often iatrogenic/from vein striping procedure or cardiac harvest)

Common peroneal nerve

  • At the lateral knee (Fibular head syndrome)
  • At the lower leg (can be from chronic exertional compartment syndrome)
  • Also, peroneal muscle herniation
  • At the ankle (Anterior tarsal tunnel syndrome)

Tibial nerve

  • At the posterior calf (Soleal sling syndrome)
  • At the medial ankle (Tarsal tunnel syndrome)

How is it diagnosed?

Peripheral nerve entrapment is often diagnosed on examination with patients complaining of numbness, tingling or weakness of the areas and muscles that that nerve supplies. This can be confirmed with electromyography and nerve conduction testing; however, these tests may provide a false negative result, as some nerves are pinched with movement called “dynamic impingement”.

Recent studies have increasingly shown the use of ultrasound as effective to evaluate and manage patients with peripheral nerve entrapment. (33-37) Diagnostic ultrasound has been shown to be as accurate as EMG/NCS with the diagnosis of some nerve entrapment syndromes. (33-37)  Common findings on ultrasound in the setting of nerve entrapment are that of nerve enlargement, focal median nerve constriction, reduced median nerve gliding (dynamically), TCL bowing, flexor tenosynovitis, or space-occupying lesions (eg, ganglia, tumors, thrombosed or anomalous arteries, abnormal muscle slips, or supernumerary muscles or tendons). (32-34,37,38)   Furthermore, The dynamic nature of ultrasound allows the provider to identify impingement that is related to motion, that may otherwise go missed on imaging or nerve testing, such as a muscle herniation (supinator syndrome) or a snapping nerve (Ulnar nerve).  It can also help delineate anatomical variants, such as a bifid (split median nerve) or a nerve going through a ligament, like the lateral femoral cutaneous nerve (inguinal ligament). 

How is it treated?

Often the most effective treatment of peripheral nerve entrapments is figuring out what the offending agent is and reducing, modifying, or eliminating it. Often this may be work/occupationally related, or can be related to workout frequency, equipment, and/or technique. Bracing and padding can also be used to help with peripheral nerve entrapments. 

For patients that fail conservative measures, they may consider an injection under ultrasound guidance to try and alleviate the symptoms in conjunction with the conservative measures mentioned above. 

For patients that fail both, ultrasound guided or traditional open releases (depending on the nerve) may provide benefit. See also section on ultrasound guided carpal tunnel release.

What is ultrasound guided nerve hydrodissection?

This involves using ultrasound to guide a needle to the area of nerve entrapment/enlargement. Then normal saline or dextrose (neuroprolotherapy) is used to hydrodissect around the nerve, to increase nerve glide.

Research has shown that ultrasound guided hydrodissection has been beneficial in case reports of multiple different peripheral nerve entrapments. (39-47) Furthermore, cadaveric studies had demonstrated increased glide when this is performed around the median nerve at the carpal tunnel. (48)

The procedure itself is done in the office with the use of local anesthesia in under 2-3 minutes. (Watch an example of median nerve hydrodissection performed successfully by Dr. Pourcho, DO)

What is the recovery like?

Typically, the area of the nerve is numb or weak or both (depending on the type of nerve) for about 4-6 hours after injection, followed by 2-3 days of dull ache. Most patients start experiencing relief after 2-3 weeks. Often as indicated in the literature and anecdotally the injection will have to be repeated several (2-3 or more) times to achieve relief goals. 

What are the risks/complications?

As with any injection, there is always an extremely low risk of infection, that the injection will not work or not provide relief, or that there is neurovascular injury. The risk of neurovascular injury is lessened with the use of ultrasound guidance.


See the full list of Dr. Pourcho's reference publications on this topic

Research articles

Minimally Invasive Ultrasound-Guided CarpalTunnel Release: Preliminary Clinical Results

Henning PT, Yang L, Awan T, Lueders D, Pourcho AM.J Ultrasound Med. 2018Nov;37(11):2699-2706. doi: 10.1002/jum.14618. Epub 2018 Apr 2.PMID: 29608024 

Sonographic Changes After Ultrasound-Guided Release of theTransverse Carpal Ligament: A Case Report.

Latzka EW, Henning PT, Pourcho AM.PM R. 2018Oct;10(10):1125-1129. doi: 10.1016/j.pmrj.2018.02.018. Epub 2018 Mar 6.PMID: 29518589

Evidence For Ultrasound-Guided Carpal Tunnel Release

Wise A., Pourcho AM, P.T. Henning, Latzka EW. - Review ­– Archives of PM R, 2020