INTRODUCTION• Wilhelm Erb is well known for his early contributions to the field of

neurology and was an eminent physician of his time. One area described by him and that still bears his name is Erb's point. This point located just superior to the clavicle was used by Erb to transcutaneously elicit contractions of various proximal arm muscles with electrical stimulation. Many have mistakenly interchanged the terms "Erb's point" and "nerve point" when describing the point of emergence of the cutaneous branches of the cervical plexus near the posterior border of the sternocleidomastoid muscle

• Before discussing the erb’s point in detail lets discuss the anatomic structures related to this poi first.

CERVICAL PLEXUSFORMATION

The cervical plexus is formed by the ventral rami of the upper six cervical nerves.It lies at the level of the first four vertebrae, deep to the internal jugular vein, and the sternocleidomastoid muscle, in front of the scalenus medius and levator scapulae.

BRANCHES:- Branches of the plexus may be divided into two sets :1. SUPERFICIAL BRANCHES consisting of those perforating the cervical

fascia and supply the integument. These are further subdivided into – ASCENDING BRANCHES DESCENDING BRANCHES

2. DEEP BRANCHES are distributed to the muscles. These are further subdivided into – MEDIAL BRANCHES LATERAL BRANCHES

SUPERFICIAL ASCENDING BRANCHES

1. LESSER OCCIPITAL2. GREATER AURICULAR3. TRANSVERSE (ANTERIOR) CUTANEOUS

THE LESSER OCCIPITAL NERVE:-Arises from the second cervical nerve.It sends off an auricular branch which supplies the skin of the upper third of the craniasurface of the auricle, and also it communicates with the posterior auricular branch of the facial nerve.

THE GREATER AURICULAR NERVE:-It’s the largest of the ascending branches.It arises from the second and third cervical nerves.When it passes on to the parotid it further divides into:- ANTERIOR BRANCH which is distributed to the skin of the face over the parotid gland,

and communicates within the substance of the gland with the facial nerve. POSTERIOR BRANCH which supplies the skin over the mastoid process and on the back

of the auricle. Some fibers also pierce the auricle, to supply the lobule and the auricle.

THE TRANSVERSE (ANTERIOR) CUTANEOUS NERVESArises from the second and the third cervical nerves.It divides beneath the platysma into the following branches –

ASCENDING BRANCHES - pass upwards to the submandibular region, and forms a plexus with the cervical branch of the facial nerve, beneath the platysma, those branches which pierce the muscle supply the upper and the front parts of the neck.

DESCENDING BRANCHES - pierce the platysma, and are distributed to the skin of the side and front of the neck as low as the sternum.

SUPERFICIAL DESCENDING BRANCHES

SUPRACLAVICULAR NERVES:-These nerves arise from the third and the fourth cervical nerves, and at the level of the clavicle divide into the following branches –

1. MEDIAN SUPRACLAVICULAR NERVES – Supply the skin as far as the median plane and as low down as the second rib,

and supply one or two filaments to the sternoclavicular joint.

2. INTERMEDIATE SUPRACLAVICULAR NERVES – Supply the skin over the pectoralis major and deltoid upto the level of the

second rib.

3. LATERAL SUPRACLAVICULAR NERVES – Supply the skin of the upper and posterior parts of the shoulder.

DEEP BRANCHES – MEDIAL SERIES

These include the following communicating and muscular branches:-COMMUNICATING BRANCHES consists of filaments which pass from the loop between first and second cervical nerves to the Hypoglossal (which further has three branches)• meningeal• superior root of ansa cervicalis• nerve to thyrohyoid and geniohyoidvagussympathetic

MUSCULAR BRANCHES to – Rectus capitis lateralisRectus capitis anteriorLongus capitisLongus colliInferior root of ansa cervicalisphrenic

DEEP BRANCHES – LATERAL SERIES

These include the following communicating and muscular branches:-

COMMUNICATING BRANCH with Accessory nerve in the substance of the sternocleidomastoid , in the posterior triangle and under the cover of the trapezius

MUSCULAR BRANCHES to – Sternocleidomastoid trapeziusLevator scapulaeScalenus medius

ERB’S POINT

ERB’S POINT or PUNCTUM NERVOSUM is a site at the lateral root of the brachial plexus.

It is a landmark of the brachial plexus on the upper trunk, located about 1 inch (2.5 cm) above the clavicle at about the level of sixth cervical vertebra.

It is formed by the union of the C5 and C6 nerve roots, which later converge.

At the nerve trunk, branches of the suprascapular nerves and the nerve to the subclavius also merge.

The merged nerve divides into the anterior and posterior division of C5 and C6.

LOCATION OF ERB’S POINT

A crucial landmark in the POSTERIOR TRIANGLE OF THE NECK is the erb’s point.

The SPINAL ACCESSORY GREATER AURICULAR LESSER OCCIPITAL & TRANSVERSE CERVICAL NERVESAll pass within 2 cm above or below this location.

The approximate location of the erb’s point is on the posterior border of the sternocliedomastoid muscle, midway between its attachments to the mastoid process and the sternum and clavicle.

The point is approximately the location of an angle between the posterolateral border of the sternocleidomastoid muscle and the clavicle.

IMPORTANCE OF ERB’S POINT

At the erb’s point , the cutaneous branches of the cervical plexus emerge from behind the posterior border of the sternocleidomastoid muscle.

Anesthesia of skin of the neck and upper chestcan be attained by blocking the cutaneous nerves as they emerge at ths point.

ERB’S PALSY• Erb's palsy (Erb-Duchenne Palsy) is a paralysis of the arm caused by injury

to the upper group of the arm's main nerves, specifically the upper trunk C5-C6 is severed. These form part of the brachial plexus, comprising the ventral rami of spinal nerves C5-C8, and T1.[1][2][3] These injuries arise most commonly, but not exclusively, from shoulder dystocia during a difficult birth.[4] Depending on the nature of the damage, the paralysis can either resolve on its own over a period of months, necessitate rehabilitative therapy, or require surgery.[

STERNOCLEIDOMASTOID MUSCLE

Also known as the sternomastoid It’s a paired muscle in the superficial layer of the anterior portion of neck.It passes obliquely down across the side of the neck and forms a prominent landmark especially when contracted.

ORIGIN – Below the sternocleidomastoid has two heads :-MEDIAL HEAD – which is a rounded tendinous fasciculus, attached to the upper part of the anterior surface of the manubrium sterni.It passes upwards, laterally, and backwards.LATERAL HEAD – is composed up of a muscular and fibrous fasiculi.It passes almost vertically upwards from the upper surface of the medial surface of the clavicle.The two heads are separated by a triangular interval.

INSERTION –Above the muscle is inserted by a strong tendon into the lateral surface of the mastoid process( from its apex to its superior border ), and by a thin apponeurosis into the superior nuchal line.The clavicular fibers are chiefly attached to the mastoid processThe sternal fibers are more oblique and superficial and extend onto the occiput.

ANTERIOR AND POSTERIOR TRIANGLES OF THE NECK

Boundaries of the anterior triangle:-

IN FRONT – by the median line of the neckABOVE – base of the mandible, and a line continuing this from the angle of the mandible to the sternocliedomastoid.BEHIND – anterior border of sternocleidomastoidAPEX - of the triangle is at the upper border of sternum.

Boundaries of the posterior triangle:-

IN FRONT – posterior border of sternocleidomastoid.BELOW – middle third of the clavicle.BEHIND – anterior margin of trapezius.APEX – corresponds to the meeting of sternocleidomastoid and trpezius on the occipital bone.