Klumpke’s palsy, named after the neuroanatomist Augusta Déjerine-Klumpke who first described it, is when there is muscle paralysis in the hand, caused by nerve damage. This causes all the fingers to stay in a flexed position so it’s also called “total claw hand.”

Now, we have 31 pairs of spinal nerves which branch off the spinal cord.

These are grouped into eight pairs of cervical nerves, twelve pairs of thoracic nerves, five pairs of lumbar nerves, five pairs of sacral nerves, and one pair of coccygeal nerves.

Now, some of the cervical and thoracic nerves form the brachial plexus, which is a network of nerves that controls the muscles and sensations in the shoulder, arm, and hand.

In terms of anatomy, the brachial plexus is divided into five roots, which come from the last four cervical nerves - C5, C6, C7, and C8 - as well as the first thoracic nerve or T1.

The five roots combine to form three trunks: C5 and C6 merge to form the superior or upper trunk, C7 remains as the middle trunk, and C8 and T1 merge to form the inferior or lower trunk.

These trunks then form six divisions, which will regroup with each other to form three cords.

These cords give off five terminal branches.

The main three are the median nerve - which is made up of contributions from C5, C6, C7, C8, and T1 - the radial nerve, which is made up of contributions from C5, C6, C7, C8, and T1, and finally, the ulnar nerve, which is made up of contributions from C8, T1, and occasionally C7.

Klumpke’s palsy occurs when there’s a stretch or tear at the the C8 or T1 roots, or at the lower trunk. This happens when an abducted arm is pulled further away from the body.

In infants, this could happen when the baby is pulled out of the birth canal by the arm during delivery.

In adults a trauma to the shoulder, like when someone tries to grab a tree branch while falling, can cause the nerves to be torn. This leads to dysfunction of the median and ulnar nerves since they contain fibers from these roots.

Okay, if we look at the effects of the nerve damage, in the forearm, the ulnar nerve innervates flexor carpi ulnaris, which controls the muscles that flex the wrist.

So when the ulnar nerve is damaged, it causes the wrist to stay extended.

On the other hand, the median nerve innervates pronator teres and pronator quadratus, which pronate the forearm, turning the palm posteriorly.

So when the median nerve is damaged, the forearm stays supinated, meaning that the palm of the hand faces anteriorly.

Now, moving onto the hand. The median nerve innervates the thenar muscles, which control the movements of the thumb, so thumb movements are limited.

Similarly, the ulnar nerve supplies the hypothenar muscles, which control the little finger, and the interossei muscles, which abduct and adduct the fingers, meaning to spread or bring them together.

So, an injury to the ulnar nerve causes a loss of movement of the little finger, and the inability to abduct or adduct all four fingers.

Finally, both ulnar and median nerve innervate the lumbricals, which are four muscles that extend the fingers at the interphalangeal joints, and keep them flexed at the metacarpophalangeal joints.

On the contrary, muscles of the forearm opposes the action of the lumbricals. These muscles include flexor digitorum profundus, which flexes the fingers at the interphalangeal joints, and extensor digitorum, which hyperextend them at the metacarpophalangeal joint.

When the ulnar and median nerves get damaged, muscles in the forearm override the action of the lumbricals, causing the hand to look like a claw.

So, with klumpke’s palsy, we end up with a person who’s forearm is stuck in the supinated position, with the wrist extended. The fingers are flexed at the interphalangeal joints, and can’t abduct or adduct.

Video - Klumpke paralysis

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