Dr Shams Amir

Pronator Syndrome

Pronator syndrome describes compression of the median nerve around the elbow or proximal forearm.

Because the same median nerve is involved in carpal tunnel syndrome, the two conditions can produce overlapping symptoms and may sometimes occur together.

What does pronator syndrome feel like?

Patients may experience:

Unlike classical carpal tunnel syndrome, symptoms may be relatively mild after rest and progressively appear during activity.

A pattern I look for in my clinical practice

I often ask patients where their symptoms begin.

In my clinical practice, patients with carpal tunnel syndrome more commonly describe numbness beginning at the fingertips.

In some patients with proximal median nerve compression, I find that symptoms are more prominent in the palm or forearm before extending towards the fingers.

I also find that some patients with pronator syndrome have relatively few symptoms during sleep or first thing in the morning.

Their symptoms progressively develop after using the arm and hand for several hours and may be most noticeable in the afternoon or evening.

Some patients describe having to stop their activity because of aching, numbness or weakness. After resting, the symptoms improve, only to return after they resume activity.

These are clinical patterns that I find useful during assessment. They should not be regarded as diagnostic tests on their own.

Where can the median nerve become compressed?

Potential sites of proximal median nerve compression include structures around the:

More than one area may contribute to compression.

What is Lacertus Syndrome?

Lacertus syndrome refers to compression of the median nerve beneath the lacertus fibrosus at the front of the elbow.

The lacertus fibrosus, also known as the bicipital aponeurosis, is a fibrous structure extending from the biceps tendon across the proximal forearm.

The term “lacertus syndrome” is increasingly used to describe a particular form of proximal median nerve compression.

There is considerable overlap between lacertus syndrome and the broader diagnosis of pronator syndrome, and the terminology is not used uniformly by all surgeons.

Lacertus syndrome or pronator syndrome?

There are different approaches among hand surgeons to proximal median nerve compression.

Some surgeons regard compression beneath the lacertus fibrosus as a distinct condition — lacertus syndrome — and advocate a targeted release of the lacertus fibrosus when the clinical findings localise the compression to this level.

I tend to consider the lacertus fibrosus as one of several potential sites of proximal median nerve compression.

Other possible sites include the pronator teres and the fibrous arch of the flexor digitorum superficialis.

In my clinical practice, I therefore try to determine whether the patient’s symptoms and examination findings suggest compression predominantly at the lacertus fibrosus or whether there may be involvement at more than one level.

This distinction can become particularly important when surgery is considered.

A targeted lacertus release may be appropriate in selected patients, while other patients may require assessment and decompression of additional potential compression sites.

Because proximal median nerve compression can produce symptoms similar to carpal tunnel syndrome — and the two can coexist — I assess the median nerve along the upper limb rather than assuming that median-nerve symptoms originate only at the wrist.

How is pronator syndrome diagnosed?

Diagnosis relies heavily on the clinical history and physical examination.

I examine along the course of the median nerve and look for specific areas where direct pressure reproduces the patient’s forearm pain, numbness or tingling.

I also assess strength and compare the affected and unaffected upper limbs.

Patients do not always recognise subtle weakness themselves. Sometimes it becomes apparent only when strength is compared directly between both sides.

Pronator syndrome can be difficult to demonstrate on conventional investigations.

Nerve conduction studies may be normal and can sometimes be more useful for identifying associated carpal tunnel syndrome than for confirming pronator syndrome itself.

In selected patients, I use dynamic ultrasound to examine the nerve during movement and look for possible sites of compression.

A normal scan does not necessarily exclude a clinically significant nerve entrapment.

In my clinical practice, I have found that patients with convincing clinical findings but no definite dynamic compression on ultrasound often respond well to conservative treatment. A clearly demonstrated area of dynamic compression may influence subsequent treatment decisions. These are my own clinical observations rather than an established diagnostic or prognostic rule.

Could the symptoms originate higher up?

Yes.

When symptoms involve several nerve distributions rather than a single peripheral nerve, I also consider more proximal causes.

These include cervical nerve pathology and conditions affecting the brachial plexus, including neurogenic thoracic outlet syndrome.

How is pronator syndrome treated?

I generally begin with non-surgical treatment.

This may include:

In my practice, physiotherapy involves assessing the whole upper limb rather than treating only the point where the patient feels symptoms.

This may involve identifying tight muscles, stiff joints and other areas that could contribute to irritation along the course of the nerve.

If symptoms remain significant despite appropriate conservative treatment, surgical decompression may be considered.

Pronator syndrome and carpal tunnel syndrome

These conditions should not automatically be regarded as mutually exclusive.

Some patients may have compression of the median nerve at more than one level.

This is one reason why persistent symptoms after treatment directed only at the wrist deserve reassessment of the entire upper limb.