In the Erb’s point or punctum nervosum, sensitive nerve branches from the cervical plexus come to the surface together. The anatomic region has played a role in local anesthesia before neck surgery since it was first described. Because the Erb point is located at the posterior border of the sternocleidomastoid muscle, it may have pathologic relevance in the setting of compression syndromes.
What is the Erb’s point?
Wilhelm Heinrich Erb was a German neurologist who made important contributions to modern neurology. Erb is the namesake of several anatomical regions. Three points of the body are called Erb points in his honor. One of these is the so-called punctum nervosum, which is an important reference point in the topographic anatomy of the neck. The sensitive nerve branches from the cervical plexus enter the surface together here at the posterior border of the sternocleidomastoid muscle in the lateral triangle of the neck. The nerves emerging from the depth at Erb’s point are known as the nervus occipitalis minor, nervus auricularis magnus, nervus transversus colli, and nervi supraclaviculares. Distinguished from the punctum nervosum are the other Erb’s points. One of them is located three centimeters above the clavicle and behind the large head turn. Erb described the point at the end of the 19th century in papers on electrotherapy. In addition, an auscultation point above the heart named after Erb should be distinguished from the punctum nervosum, from which all heart sounds and murmurs can be heard.
Anatomy and structure
At the punctum nervosum or Erb’s point, the nerve branches nervus occipitalis minor, nervus auricularis magnus, and nervus transversus colli and nervi supraclaviculares emerge from deep within the body to the surface. The point is topographically located next to the great cephalic inverted nerve, which is located on the side of the neck. The emerging nerves are sensitive nerves. Their exact breakthrough point corresponds to the upper portion of the lateral triangle of the neck. The nerve branches run in close proximity to each other at the Erb point and pass through the sternocleidomastoid muscle at the posterior border. In addition to the cervical muscles and nerves, various vessels are located in close proximity to the punctum nervosum. The sensory nerves of the punctum nervosum are the cutaneous nerves of the cervical plexus, which take different directions after passing through to the surface. The nervus occipitalis minor travels upward along the back of the head, the nervus auricularis magnus travels toward the ear, and the nervus transversus colli travels horizontally along the neck. In contrast, the supraclavicular nerves pull caudally.
Function and Tasks
The Erb point in terms of the punctum nervosum is one of the most important reference points in topographic neck anatomy. The point corresponds, mutatis mutandis, to an agglomeration point of nerve branches of the cervical plexus and allows the individual nerves to pass through to their destination. The minor occipital nerve relevant to the Erb point is better known as the lesser occipital nerve and accordingly plays a role in the sensory innervation of the back of the head. The skin sections above the parotid gland and at the back of the ears are in turn sensitively innervated by the auricular magnus nerve, which also passes through the Erb’s point. The transverse collateral or transverse cervical nerve, which also passes through the punctum nervosum, provides sensory innervation to the throat, and the supraclavicular nerves innervate the regions above the clavicle. Ultimately, the punctum nervosum itself performs no active function. Nevertheless, it is a crucial body site because the region allows the safe passage of the sensitive nerves and thus passively secures the sensitive innervation of the clavicle region, ear region, occiput, and throat. Although the Erb point is anatomically designed in principle to allow the nerves to come to the surface with as little compression as possible, the region becomes a bottleneck in many cases. The point also plays a role in anesthesia from a clinical perspective. Local anesthesia of the region allows for invasive procedures in the neck. Placement of local anesthesia in the punctum nervosum turns off several sensitive nerves at the same time. In this way, pain sensations reach the nerve endings but are no longer transported to the central nervous system via afferent pathways. The patient’s conscious perception of pain is thus switched off.For operations in the neck region, these relationships have played an increased role since Wilhelm Erb first described the point.
Diseases
The punctum nervosum may acquire pathologic relevance. In most cases, this pathological relevance is due to compression syndromes. In this context, the term thoracic-outlet syndrome is particularly relevant. In modern medicine, all neurovascular compression syndromes that occur at the upper thoracic aperture are subsumed under this term. Thiracic-outlet syndromes include costoclavicular syndrome, scalenus syndrome, and hyperabduction syndrome, pectoralis minor syndrome, and shoulder-arm syndrome or Paget-von-Schroetter syndrome. TOS involve compression of the brachial plexus by skeletal, muscular, or fibrous anatomic structures of the upper thoracic aperture, which can result in neurologic, arterial, and venous symptoms. Compression is not uncommon in the punctum nervosum, with neurologic symptoms predominating in this case. Sensory disturbances in the area of the neck, clavicle, back of the head, ears and throat present themselves in case of Erb’s point near compression of the sensitive nerves. That Erb’s point is so susceptible to compression is due to its proximity to the sternocleidomastoid muscle. Compressions are particularly common in hyperplasia of the muscle. In addition, mechanical force on the Erb’s point can cause pressure damage to the four sensitive nerves that meet in the region. This phenomenon is often preceded by an accident.