Ulnar nerve
By : Mohammed WaelGeneral
It is the largest terminal branch of the brachial plexus .
It originates from the anterior division of the medial cord of brachial plexus .
It runs through axilla , arm and forearm to reach the hand where it terminate by dividing into medial and lateral terminal divisions .
Its fibers are from the anterior rami of spinal nerves C8 and T1, but sometimes they have fibers of C7 fibers also .
It contains both sensory fibers which give sensory supply to part of hand and motor fibers which give motor supply to some muscles of forearm ( two muscles ) and most of the intrinsic hand muscles .
It originates from the anterior division of the medial cord of brachial plexus .
It runs through axilla , arm and forearm to reach the hand where it terminate by dividing into medial and lateral terminal divisions .
Its fibers are from the anterior rami of spinal nerves C8 and T1, but sometimes they have fibers of C7 fibers also .
It contains both sensory fibers which give sensory supply to part of hand and motor fibers which give motor supply to some muscles of forearm ( two muscles ) and most of the intrinsic hand muscles .
Course & Relation
In axilla
After arising from the brachial plexus, the ulnar nerve descends in axilla lateral to the axillary artery and medial to the axillary vein.
In arm
It leaves the axilla at the lower border of the teres major where it passes medial to the brachial artery ( the brachial artery is the continuation of the axillary artery ) up to the middle of arm where it penetrates the medial intermuscular septa of arm ( thickness of deep fascia which divides the arm into tow compartments one anterior and one posterior ) after penetrating the septa it enters the posterior compartment of arm where it is accompanied by inferior ulnar collateral artery ( which is branch of the brachial artery ) .Then it passes behind the medial epicondyle of humerus through the ulnar tunnel ( small space between the medial epicondyle and olecranon) so the ulnar nerve here is superficial and easily palpable , and vulnerable to injury . Here it gives articular branch to the elbow joint .
In forearm
It leaves the ulnar tunnel to pierce the two heads of the flexor carpi ulnaris .Then it passes to the flexor carpi ulnaris alongside the ulna.
The main branches of the ulnar nerve in the forearm are
1.Muscular branch – which innervates two muscles in the anterior compartment of the forearm.
2.Palmar cutaneous branch – which innervates the medial half of the palm.
3.Dorsal cutaneous branch – which innervates the dorsal surface of the medial one and a half fingers, and the associated dorsal hand area.
The main branches of the ulnar nerve in the forearm are
1.Muscular branch – which innervates two muscles in the anterior compartment of the forearm.
2.Palmar cutaneous branch – which innervates the medial half of the palm.
3.Dorsal cutaneous branch – which innervates the dorsal surface of the medial one and a half fingers, and the associated dorsal hand area.
In hand
It leaves the forearm by emerging from deep to the tendon of the flexor carpi ulnaris
It turns medial to the ulnar artery ( according to general rule that says that nerves runs to the outside in relation to arteries in the forearm ).It runs superficially to the flexor retinaculum by passing through the Guyon’s canal ( ulnar canal ) and here the ulnar nerve is lateral to the pisiform and medial to the artery .The ulnar nerve ends a the flexor retinaculum(t the distal border) by dividing into superficial and deep terminal branches .
It turns medial to the ulnar artery ( according to general rule that says that nerves runs to the outside in relation to arteries in the forearm ).It runs superficially to the flexor retinaculum by passing through the Guyon’s canal ( ulnar canal ) and here the ulnar nerve is lateral to the pisiform and medial to the artery .The ulnar nerve ends a the flexor retinaculum(t the distal border) by dividing into superficial and deep terminal branches .
Muscular branches of ulnar nerve
1- I n forea rm : it gives motor branch to two muscles in the anterior compartment of forearm .
A- Flexor carpi ulnaris – flexes and adducts the hand at the wrist
B- Flexor digitorum profundus (medial half ) flexes the ring and little
fingers at the distal interphalangeal joint .
The remaining muscles of the forearm are innervated by the median nerve .
2- In the ha nd : the majority of the intrinsic hand muscles are innervated by the deep branch of the ulnar nerve :
1.Hypothenar muscles (flexor digit minimi brevis, abductor digiti minimi, opponens digiti minimi)
2.Medial two lumbricals
3.Adductor pollicis
4.Palmar and dorsal interossei of the hand.
Note: the palmaris brevis muscle is not innervated by the deep branch and it is an exception which is innervated by the superficial branch of the ulnar nerve. The other muscles of the hand ( lateral two lumbricals and the thenar eminence ) are innervated by the median nerve .
A- Flexor carpi ulnaris – flexes and adducts the hand at the wrist
B- Flexor digitorum profundus (medial half ) flexes the ring and little
fingers at the distal interphalangeal joint .
The remaining muscles of the forearm are innervated by the median nerve .
2- In the ha nd : the majority of the intrinsic hand muscles are innervated by the deep branch of the ulnar nerve :
1.Hypothenar muscles (flexor digit minimi brevis, abductor digiti minimi, opponens digiti minimi)
2.Medial two lumbricals
3.Adductor pollicis
4.Palmar and dorsal interossei of the hand.
Note: the palmaris brevis muscle is not innervated by the deep branch and it is an exception which is innervated by the superficial branch of the ulnar nerve. The other muscles of the hand ( lateral two lumbricals and the thenar eminence ) are innervated by the median nerve .
Clinical Relevance:
Froment’s sign is a test for ulnar nerve palsy specifically paralysis of the adductor pollicis
1.The patient is asked to hold a piece of paper between the thumb and index finger, as the paper is pulled away.
2.They should be able to hold the paper there with no difficulty (via adduction of the thumb).
When the patient is unable to adduct his thumb that means he is positively tested to Froment’s sign test.
Instead of adduction, they do flexion(thumb flexion) at the interphalangeal joint trying to hold the paper.
1.The patient is asked to hold a piece of paper between the thumb and index finger, as the paper is pulled away.
2.They should be able to hold the paper there with no difficulty (via adduction of the thumb).
When the patient is unable to adduct his thumb that means he is positively tested to Froment’s sign test.
Instead of adduction, they do flexion(thumb flexion) at the interphalangeal joint trying to hold the paper.
Sensory Branches Of Ulnar Nerve
The ulnar nerve gives three sensory branches which are : 1-palmar cutaneous branch : which supplies sensation to medial one half of palm ( it arises in the forearm ) .
2-dorsal cutaneous branch : which supplies sensation to medial one half of dorsum of hand and dorsum surface of the medial one and half fingers( it arises in the hand ).
3-superficial branch: which innervates the palmar surface of the medial one and half fingers (it arises in the hand ) .
2-dorsal cutaneous branch : which supplies sensation to medial one half of dorsum of hand and dorsum surface of the medial one and half fingers( it arises in the hand ).
3-superficial branch: which innervates the palmar surface of the medial one and half fingers (it arises in the hand ) .
Clinical Relevance:
Ulnar Nerve Palsy
Damage at the Elbow
Mechanism of injury: Trauma at the level of the medial epicondyle (e.g. isolated medial epicondyle fracture, supracondylar fracture). It also can be compressed in the cubital tunnel.
A.Motor functions
1.All the innervated muscles by the ulnar nerve are affected.
2.Wrist flexion still can be occurred, but it is accompanied by abduction ,because of the paralysis of
A.Flexor carpi ulnaris
B.Flexor digitorum profundus(medial half )
3.Fingers abduction and adduction cannot be occurred, because of the interossei paralysis
4.Movement of the 4th and 5th digits is ruined, because of the paralysis of
A.Lumbricals(medial two) b.Hypothenar muscles
5. Thumb adduction is also ruined. The patient is going to have a positive Froment’s sign because of the paralysis of adductor pollicis.
B.Sensory functio ns
loss of sensation over medial third of hand ( palm , dorsum of hand and digits ).
Symptoms
1.The patient cannot grip paper placed between fingers, (positive Froment’s sign)
2.wasting of hypothenar eminence.
Mechanism of injury: Trauma at the level of the medial epicondyle (e.g. isolated medial epicondyle fracture, supracondylar fracture). It also can be compressed in the cubital tunnel.
A.Motor functions
1.All the innervated muscles by the ulnar nerve are affected.
2.Wrist flexion still can be occurred, but it is accompanied by abduction ,because of the paralysis of
A.Flexor carpi ulnaris
B.Flexor digitorum profundus(medial half )
3.Fingers abduction and adduction cannot be occurred, because of the interossei paralysis
4.Movement of the 4th and 5th digits is ruined, because of the paralysis of
A.Lumbricals(medial two) b.Hypothenar muscles
5. Thumb adduction is also ruined. The patient is going to have a positive Froment’s sign because of the paralysis of adductor pollicis.
B.Sensory functio ns
loss of sensation over medial third of hand ( palm , dorsum of hand and digits ).
Symptoms
1.The patient cannot grip paper placed between fingers, (positive Froment’s sign)
2.wasting of hypothenar eminence.
Damage at the Wrist
Mechanism of injury: the anterior wrist tear.
Motor functions
1.The intrinsic muscles of the hand are affected only.
2. Fingers abduction and adduction cannot be occurred because of the paralysis of the interossei.
3.Movement of the 4th and 5th digits is ruined because of the paralysis of the medial two lumbricals and hypothenar muscles.
4.Thumb Adduction is ruined, and the patient is going to have a positive Froment’s sign because of the paralysis of adductor pollicis
Sensory functions
The palmar and superficial branches are usually damaged, but the dorsal branch is unaffected, which results in the loss of sensation over the medial one and a half fingers(palmar side only).
Symptoms
1.The patient cannot grip paper placed between fingers, (positive Froment’s sign)
2.wasting of hypothenar eminence.
3.It causes claw hand due to paralysis of third & fourth lumbricals which leads to extension of metacarpophalangeal joints & flexion of interphalangeal joints of little & ring fingers.
Motor functions
1.The intrinsic muscles of the hand are affected only.
2. Fingers abduction and adduction cannot be occurred because of the paralysis of the interossei.
3.Movement of the 4th and 5th digits is ruined because of the paralysis of the medial two lumbricals and hypothenar muscles.
4.Thumb Adduction is ruined, and the patient is going to have a positive Froment’s sign because of the paralysis of adductor pollicis
Sensory functions
The palmar and superficial branches are usually damaged, but the dorsal branch is unaffected, which results in the loss of sensation over the medial one and a half fingers(palmar side only).
Symptoms
1.The patient cannot grip paper placed between fingers, (positive Froment’s sign)
2.wasting of hypothenar eminence.
3.It causes claw hand due to paralysis of third & fourth lumbricals which leads to extension of metacarpophalangeal joints & flexion of interphalangeal joints of little & ring fingers.
Handlebar neuropathy
pressure on the hooks of the hamate ( hamate is one of the carpal bones ) can occur with people who ride long distance on bicycle with their hands in an extended position against the hand grips , this causes a compression on the ulnar nerve .
The results of this compression have the same signs of injury of ulnar nerve just above the wrist .
The results of this compression have the same signs of injury of ulnar nerve just above the wrist .
References
1. Keith L. Moore , Arthur F. Dalley A. M. R. Agur; Moore clinically oriented anatomy7thedition;pp.682,685,686,717,729,739,749, 761-764,769-770,786-787
2. Dr. Lawrence E. Wineski,PhD;SNELLIS CLINICAL ANATOMY BY REGIONS 10th edition;ch3;pp.226,229,271,291,293,309,321,332, 339,343,346-348,361-365
3. Ulnar Nerve; Queen's University Belfast; Anatomical basis of clinical practice 1; 2018/2019; StuDocu;https://www.studocu.com /en-gb/document/queens-university-belfast/anatomical-basis-of- clinical-practice-1/ulnar-nerve/19196863
4. Ulnar Nerve; Physiotherapy Clinic; December 12, 2019; Mobile Physiotherapy Clinic; https://mobilephysiotherapyclinic.in/ulnar- nerve/
5. The Ulnar Nerve;Oliver Jones; TeachMeAnatomy; https://teachmeanatomy.info/upper-limb/nerves/ulnar-nerve/
6. Ulnar nerve; Shahab Shahid,MBBS;Kenhub; https://www.kenhub.com/en/library/anatomy/the-ulnar-nerve
7. Chapter 44 - Driver’s Elbow; Steven D.Waldman,MD, JD; Sciencedirect;https://www.sciencedirect.com/science/article/pii/ B9781455709991000447
2. Dr. Lawrence E. Wineski,PhD;SNELLIS CLINICAL ANATOMY BY REGIONS 10th edition;ch3;pp.226,229,271,291,293,309,321,332, 339,343,346-348,361-365
3. Ulnar Nerve; Queen's University Belfast; Anatomical basis of clinical practice 1; 2018/2019; StuDocu;https://www.studocu.com /en-gb/document/queens-university-belfast/anatomical-basis-of- clinical-practice-1/ulnar-nerve/19196863
4. Ulnar Nerve; Physiotherapy Clinic; December 12, 2019; Mobile Physiotherapy Clinic; https://mobilephysiotherapyclinic.in/ulnar- nerve/
5. The Ulnar Nerve;Oliver Jones; TeachMeAnatomy; https://teachmeanatomy.info/upper-limb/nerves/ulnar-nerve/
6. Ulnar nerve; Shahab Shahid,MBBS;Kenhub; https://www.kenhub.com/en/library/anatomy/the-ulnar-nerve
7. Chapter 44 - Driver’s Elbow; Steven D.Waldman,MD, JD; Sciencedirect;https://www.sciencedirect.com/science/article/pii/ B9781455709991000447
