Assessment and evaluation
The symptoms of ulnar nerve compression in the two syndromes are similar even though the pathologies occur in different locations. Clients usually report pain, numbness and/or paresthesia in the ulnar nerve distribution of the hand (see hand illustration). It is important to isolate the sensory symptoms to the ulnar nerve distribution because many people assume they have carpal tunnel syndrome with neurological symptoms in the hand. Weakness in muscles supplied by the ulnar nerve may also occur in both conditions.

While the ulnar nerve innervates a number of muscles in the forearm, motor weakness is most evident in muscles of the hand, such as the adductor pollices. It is an important muscle in grasping objects. Consequently, the client may report difficulty in holding objects in the hand, or clumsiness when performing precision activities such as writing.

While many symptoms of these two peripheral neuropathies are similar, there are a number of factors that help distinguish them in the evaluation process. If the symptoms started from an acute injury, identify whether the primary insult was to the elbow or the wrist. In chronic compression pathologies it is a little more complex, but a more thorough assessment provides valuable clues.

If the symptoms are aggravated by long periods with the body weight resting on the wrist, especially if it is in a hyperextended position, Guyon’s canal syndrome is implicated. Using a cane for walking is an example of how chronic compression may occur in Guyon's canal. If the symptoms occur from long periods of resting the body weight on the elbows, or holding the elbows in a flexed position (not necessarily weight-bearing) for long periods, then cubital tunnel syndrome is more likely.

There are a few visual indicators that may help identify ulnar nerve compression from either cubital tunnel syndrome or Guyon’s canal syndrome. As mentioned above, the ulnar nerve innervates several muscles in the hand. Compression of the nerve in either condition may lead to atrophy of the hypothenar muscles (those located in the fleshy bundle on the ulnar side of the hand). In some cases, cubital tunnel syndrome is aggravated by a postural distortion of the upper extremity called cubital valgus (see Figure 2). In cubital valgus the nerve may be pulled taut against structures bordering it within the cubital tunnel.

Palpation is helpful for identifying both conditions. Because the region of entrapment is superficial in both pathologies, palpating the involved area may increase symptoms. If manual pressure directly over the cubital tunnel reproduces the primary complaint, then cubital tunnel syndrome is likely. Similarly, if pressure directly over Guyon's canal reproduces the complaint, Guyon’s canal syndrome is implicated.

The neurological symptoms of cubital tunnel syndrome or Guyon’s canal syndrome are apt to be reproduced with certain motions of the upper extremity. If cubital tunnel syndrome is the primary problem, neurological sensations may be reproduced with elbow flexion either passively or actively. Often the symptoms are not aggravated by simply moving the elbow into a flexed position. The elbow must be held in the flexed position for some time before symptoms recur. Attempting to recreate symptoms by holding the elbow in flexion is demonstrated during the elbow-flexion test described below.

If Guyon’s canal syndrome is the problem, pain is common with wrist hyperextension, either actively or passively. In hyperextension the nerve is pulled taut across the carpal bones, and if damaged from compression, the increased tension on the nerve will aggravate symptoms.

There are two special orthopedic tests commonly used to help identify ulnar nerve compression. The first is the elbow-flexion test. It is primarily used to identify cubital tunnel syndrome.

This test begins with the client in a standing or seated position. With the shoulder laterally rotated, the client brings the elbow into full flexion while the forearm is supinated and the wrist is hyperextended. This is the position used when carrying a tray, for example. If the condition is unilateral, it is helpful to have the client adopt the position with both sides at the same time so a comparison with the unaffected side can be made. Cubital tunnel syndrome is probable if symptoms are reproduced within about 60 seconds while holding this position.

Another test commonly used to evaluate both conditions is Froment's sign. It evaluates weakness of the adductor pollices that may result from nerve compression. While it doesn't discriminate between these two conditions, it is helpful in clarifying ulnar nerve involvement in upper-extremity neurological disorders.

In Froment's sign the client holds a piece of paper between the thumb and MCP joint of the index finger. It is best if the paper is folded several times so it does not tear easily. The practitioner attempts to pull the paper out of the client's grasp. If the client is able to hold it firmly and the practitioner has a difficult time pulling it from the client's grasp, there is no perceivable weakness in the adductor pollex muscle. If, however, the client is unable to prevent the practitioner from easily pulling the paper out (especially compared to the unaffected side), there is a good chance that motor impairment of the adductor pollex exists.