Benediction sign (or Benediction posture) is a clinical sign of ulnar neuropathy of the hand. It results in the functional impairment of the intrinsic muscles of the hand that act on the metacarpophalangeal and interphalangeal joints. The intrinsic muscles that will be affected are the interossei and lumbrical muscles. The interossei muscles normally adduct and abduct the second, third, and fourth fingers, whereas the lumbricals flex the metacarpophalangeal joints and extend the proximal and distal interphalangeal joints. As a result of ulnar neuropathy, these intrinsic muscles will lose their function, hence producing the Benediction sign (as seen in the image present at the end of the article).
This sign has also been referred to by other names in literature, such as the Preacher’s hand and “main-en-griffe.” The papal benediction sign was first recognized in historical artwork of Saint Peter, who presumably suffered from ulnar neuropathy. After him, other popes imitated his hand gesture in preaching.
Although the benediction sign has existed in historical images dating back to the second and third centuries, the exact neurological cause of this pathology has been under debate. Some clinicians and anatomists have attributed this clinical sign with median neuropathy, while others have favored the ulnar neuropathy as its etiology. However, the final hand postures, in either case, are almost similar, as discussed below.
Anatomically, the median nerve arises from the lateral and medial cords of the brachial plexus that originate from the nerve roots C5-T1. The median nerve does not have a branch in the arm. In the forearm, the median nerve mainly supplies to flexors of the forearm and the wrist. In hand, the median nerve supplies the lateral two lumbrical muscles supplying the second and third fingers and the thenar muscles. Lumbricals flex the metacarpophalangeal joints and extend the proximal and distal interphalangeal joints. The median nerve normally flexes the wrist, proximal interphalangeal joints, as well as the metacarpophalangeal and distal interphalangeal joints of the index and middle finger. Therefore, a lesion of the median nerve will affect the flexors of the second and third fingers resulting in the benediction sign when trying to make a fist. It is worth noting that the medial two lumbrical muscles supplied by the ulnar nerve will be normal. Therefore, when making a fist in these patients, the metacarpophalangeal joints of the fourth and fifth fingers will be flexed.
The ulnar nerve is derived from the medial cord of the brachial plexus, incorporating nerve roots C8-T1. When it reaches the forearm, it gives rise to motor branches that innervate the flexor carpi ulnaris and the medial half of flexor digitorum profundus. In the hand, the ulnar nerve innervates medial two lumbricals supplying the fourth and fifth fingers, the interossei muscles, and the hypothenar muscles. When relating the injury to the ulnar nerve, the benediction sign would present if a person tries to open their hand and extend the fingers. Due to the loss of function of medial two lumbricals, the metacarpophalangeal joints of fourth and fifth fingers will be in extension, while the interphalangeal joints will be in flexion.
In summary, the difference between the Benediction signs produced by ulnar and median neuropathies are:
1. In median neuropathy, the Benediction sign will be present when making a fist. The metacarpophalangeal joints and interphalangeal joints of the second and third finger will be in extended position due to the loss of action of their flexor muscles. In ulnar neuropathy, the Benediction sign will be present when opening the hand and extending the fingers. Due to the loss of function of medial two lumbricals, the metacarpophalangeal joints of fourth and fifth fingers will remain extended, while the interphalangeal joints will be in a flexed position.
2. In median neuropathy, the metacarpophalangeal joints of the fourth and fifth fingers will appear flexed due to the normal medial two lumbricals supplied by the ulnar nerve. In ulnar neuropathy, the metacarpophalangeal joints of the fourth and fifth fingers will be in extension.
Careful examination of the position of the fingers and consideration to the intention of the Pope was taken into account, as an open hand during blessing was a customary means of indicating peaceful motives. For these reasons, the ulnar nerve is regarded as the cause of the benediction sign based on observations of the history, culture, and artwork done on the of the papal lineage.
The presence of a benediction sign indicates an ulnar neuropathy. However, the diagnosis of an ulnar neuropathy depends initially on the relevant clinical history and examination. On physical examination, other clinical signs of the ulnar neuropathy are also usually observable.
Since clinical history and physical examination are subjective and imprecise. Accordingly, electromyography and nerve conduction studies, as well as ultrasound studies, are also used to confirm the diagnosis.
A neurologist often diagnoses the condition and further evaluates for neuropathy. An interprofessional team that includes a neurologist, neurosurgeon, physical therapist, hand surgeon, and nurse practitioner should be involved in further management of this condition. The specific management depends upon the underlying cause if present. Physical therapy, occupational therapy, and extensive rehabilitation with strength training are necessary for all individuals to ensure good clinical outcomes.
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