The petrosal profundal nerve is a sympathetic nerve of the head region. Its main functions include inhibitory influences on saliva and tear production. Injuries and deficits of the petrosal profundal nerve may result in salivary and lacrimal secretion disorders, among other symptoms.
What is the petrosal profundal nerve?
The internal carotid plexus corresponds to the periarterial sympathetic nerve fiber plexus of the internal carotid artery. Involved in the plexus are the nervi carotici interni of the superior cervical ganglion (ganglion cervicale superius), which form distinct structures after exiting the nerve plexus. These structures are the postganglionic fibers of the internal carotid plexus. One of these fibers is the petrosal profundal nerve. Together with other structures, this nerve passes unconnected through the ciliary ganglion as well as the pterygopalatine ganglion and from there it controls its target organs. The petrosal profundal nerve thus corresponds to a sympathetic nerve of the head region. The sympathetic nerve belongs to the autonomic nervous system and escapes voluntary control. Therefore, the fibers of the petrosal profundal nerve cannot be influenced arbitrarily. With its sympathetic fibers, the nerve innervates various tissues, such as the blood vessels of the head region in addition to the lacrimal glands. In German literature, the nerve is also called the deep petrous nerve.
Anatomy and structure
The profound petrosal nerve arises from the internal carotid plexus. From this nerve plexus near the internal carotid artery, the nervous structure travels together with the vessel into the so-called petrous bone (pars petrosa ossis temporalis), where it unites with the parasympathetic petrosal major nerve to form the canalis pterygoidei or Vidi nerve. As the canalis pterygoidei nerve, the petrosal profundus nerve passes through the wing process canal and directs the pterygopalatine ganglion. The ganglion is a collection of nerve cell bodies through which all fibers of the petrosal profundal nerve pass unconnected. The petrosal profundal nerve is switched exclusively in the cervical supercervical border ganglion. In this superior cervical ganglion between the longus capitis muscle and the digastric muscle, different sympathetic nerves are interconnected, innervating the head region and the cervical region near the head. The sympathetic root cells reach the cervical superior ganglion via the vagosympathetic truncus or the cervical part of the border cord. At this point, the petrosal profundal nerve contributes sympathetic fibers to the petrosal major nerve of the VII cranial nerve (facial nerve) and also provides fibers to the eye and ear via the ciliary ganglion. In the orbit, fibers from the petrosal profundal nerve attach to the zygomatic nerve of the maxillary nerve and continue to the lacrimal gland.
Function and Tasks
The petrosal profundal nerve delivers sympathetic fibers to the lacrimal gland and blood vessels of the head region. The structure also innervates the glandulae nasales as well as glandulae palatinae. Since the petrosal profundal nerve is additionally involved in the innervation of the orbitalis muscle, it controls venous blood return to the inferior opthalmic vein. Furthermore, as a fiber portion of the gacial nerve, it is involved in facial innervation and additionally mediates sympathetic influences on the eye and ear. Specifically, the sympathetic nerve has an inhibitory effect on the innervated glands. The glandulae palatinae are numerous salivary glands within the submucosal tissues of the posterior hard palate, soft palate, and uvula. Unlike the parasympathetic nervous system, the sympathetic nervous system prepares the body for peak performance and inhibits all bodily functions that are dispensable in the present situation. The sympathetic nervous system is the more active part of the autonomic nervous system during stress reactions and is supposed to ensure the survival of the organism by increasing the efficiency of the body and initiating a concentration on essential body processes. Since the sympathetic nervous system inhibits all dispensable body functions in stress reactions, the sympathetic fibers of the petrosal profundus nerve have an inhibitory effect on the salivary glands. On the other hand, the sympathetic nervous system has a tonus-increasing effect on the veins. The fibers of the petrosal profundal nerve therefore stimulate the venous orbital muscle to contract. These processes affect the entire cardiovascular system.
Diseases
Like any other nerve, the profound petrosal nerve can be affected by inflammatory, mechanical, or compression-related damage. Depending on the extent of damage, varying degrees of loss of function and paralysis occur within the area of supply. Since the nerve is a sympathetic nerve, the interaction between the parasympathetic and sympathetic nervous systems shifts when the structure is lesioned. This means that the tissues and organs in the area supplied by the profound petrosal nerve come under predominantly parasympathetic influence. In addition to trauma and inflammation, the cause of symptoms of failure of the profound petrosal nerve can be, for example, spatial lesions that cause bruising of the nerve. Some pathological conditions of the profound petrosal nerve can be determined by means of the Schirmer test. Ophthalmology uses this test to diagnose lacrimal secretion disorders. In the test, a litmus paper strip is inserted into the lower conjunctival sac of both eyes. The onset of tear secretion moistens the paper. After minutes, the doctor measures the distance on the strips that is wetted by tears. Ten to 20 millimeters of the paper is usually moistened after five minutes. If the wetted distance is far above or below this value, it points to a tear secretion disorder, which may indicate pathological changes in the sympathetic-parasympathetic interaction. However, lacrimal secretion disorders can also be triggered by quite a few processes without a neurogenic nature. Imaging helps in the differential diagnosis. If there is indeed a failure of the profound petrosal nerve, additional symptoms such as salivary secretion disorders or facialis disorders are usually present.
