Symptoms

Lacertus syndrome occurs when the median nerve becomes compressed at the elbow, under a fibrous expansion called lacertus fibrosus. Lacertus fibrosus runs obliquely from the tendon of the biceps to the inner side of the elbow. Lacertus fibrosus crosses and can compress the median nerve.

The manifestations of lacertus syndrome are both sensory and motor. In particular, it causes numbness, pain in the forearm that can radiate to the elbow, as well as loss of feeling, strength and dexterity. The patient often has difficulty handling small objects and notices a tendency to easily drop objects.

Symptoms: 

• Pain in the forearm, elbow and often goes up to the shoulder
• Tired or heavy sensation in the forearm 
• Muscular weakness in thumb and grip
• Clumsiness
• Loss of endurance

Unlike carpal tunnel syndrome, nocturnal symptoms are rather unusual.

Lacertus syndrome very often coexists with carpal tunnel syndrome, which is called double crush syndrome, but the condition can also present alone.

Causes

Lacertus syndrome affects both men and women, usually after 35 years of age. Manual work, overwork and repetition of movements with the forearm in pronation are recognized as risk factors.

It is estimated that a large number of people with carpal tunnel syndrome also suffer from lacertus syndrome.

Diagnosis

Because it is a rather unknown and non-documented condition, lacertus syndrome presents a particular diagnostic challenge. Its symptoms are frequently confused with those of carpal tunnel syndrome, which complicates the differential diagnosis and management of the patient.

Unfortunately, few clinicians have the knowledge to suspect and investigate lacertus syndrome. This misdiagnosis is a very common cause of carpal tunnel surgery failure.

Partial resolution or persistence of symptoms in a patient operated on for a carpal tunnel very often means that the site of the compression has not been properly identified or that there is a second area of compression.

Diagnosis is based primarily on examination and systematic physical examination of the entire upper limb, not just the wrist. The scratch collapse test is not a very well known provocative maneuver, but very useful in confirming the diagnosis. The test consists of comparing the resistance force of the lateral rotators by stimulating (scratching) the suspected compression zone.

The electromyogram (EMG) rarely detects lacertus syndrome, but can be useful in diagnosing associated carpal tunnel syndrome. It can occur on one side or be bilateral.

All patients who report numbness, tingling, muscle loss, or loss of strength, dexterity, or manual endurance should be examined and tested not only for carpal tunnel syndrome, but also for lacertus syndrome.

Because lacertus syndrome is still unknown, its diagnosis is largely based on the knowledge and experience of the clinician consulted.