Overview of the parasympathetic nerves
The parasympathetic nerves are purely motor nerves and are divided into two parts, the cerebral and spinal nerve roots, which originate from the medulla oblongata and the upper cervical cord respectively. The medulla oblongata is small and occurs from the lower part of the nucleus pulposus. The nerve fibers under the vagus nerve as 4 to 5 roots go out of the medulla oblongata laterally and merge with the spinal cord roots when they go outward to the jugular vein foramen. After exiting the skull through the jugular foramen, it separates from the spinal cord portion and joins the vagus nerve, innervating the pharyngeal muscles and the laryngeal reentrant branch of the vagus nerve, which supplies the soft palate and the intrinsic laryngeal musculature.
Etiology
1. Peripheral injury
(1) Medical-origin injury Mostly due to cervical surgery, the extracranial section of the parasympathetic nerve is injured, in which the most common injury is caused by biopsy or removal of lymph nodes in the posterior cervical triangle, with an incidence rate of 3% to 6%. The most common injury is caused by lymph node biopsy or removal in the posterior triangle of the neck, with an incidence rate of 3% to 6%. Some of these injuries occur during neck tumor removal surgery and carotid artery surgery.
(2) Skull base fracture When craniocerebral trauma skull base fracture, the fracture line through the occipital condyles and jugular foramen can cause jugular foramen section and intracranial section of the parasympathetic nerve contusion or extrusion.
(3) Gunshot wounds at the base of the skull can directly cause damage to the parasympathetic nerves.
(4) Tumor infiltration or compression, such as cervical lymph node tuberculosis, cervical malignant tumors can cause extracranial damage to the parasympathetic nerve segment; tumors in the region of the occipital foramen magnum and the pontine cerebellar angle can cause damage to the jugular foramen and intracranial segment.
(5) Other craniocervical junction malformations, arachnoiditis of the base of the skull, jugular phlebitis, and multiple encephalomyelitis can cause peripheral damage to the parasympathetic nerves.
2.Nuclear injury
Nuclear acute injury is common in the medulla oblongata hemorrhage or infarction and inflammation. Chronic injury is common in medulla oblongata and spinal cord cavernous disease, brainstem tumor, high cervical intramedullary tumor.
Symptoms
In the case of isolated injury to the spinal branch of one parasympathetic nerve or damage to its spinal cord nucleus, the ipsilateral sternocleidomastoid and trapezius muscles are paralyzed with atrophy. Because of the dominance of the contralateral sternocleidomastoid muscle, the chin is turned to the affected side when it is calm, and there is no power to turn the head to the opposite side when it is exerted, the shoulder of the affected side is drooped, and it cannot be shrugged, and the position of the scapula is skewed, and there is atrophy of the muscles innervated by it. Due to the displacement of the scapula, the brachial plexus nerve is chronically pulled, which limits the lifting and abduction of the affected side of the upper limb. In advanced stages, spastic contracture (strabismus) deformity can occur due to scar irritation. In bilateral damage, the patient has weakness in head and neck tilt and forward flexion. Paraneoplastic nerve damage caused by skull base fracture or gunshot injury, lesions in the jugular foramen region, lesions in the occipital foramen magnum region, huge lesions in the cerebral bridge cerebellar angle, and extensive lesions in the skull base, and medullary nuclear paralysis often occur simultaneously with damage to the posterior cerebral nerves and other cerebral nerves. In nuclear paralysis of the brainstem, the damage to the cerebral nerves is often multigroup and bilateral.
Examination
1. Neuroimaging
When paraneoplastic nerve injury is suspected to be caused by tumor of the skull base or brainstem lesion, CT and MRI imaging examination can help to diagnose the primary disease.
2. Electromyography
If the insertion potential of the trapezius and sternocleidomastoid muscles is obviously prolonged or there is no evoked electrical response, the diagnosis of parasympathetic nerve injury can be established.
Diagnosis
1.Localization diagnosis
(1) Diagnosis of cervical injury of spinal branch of parasympathetic nerve: discomfort, weakness or pain in the affected shoulder, difficulty in shrugging the shoulder, lifting the shoulder below 90°, sagging of the shoulder, tugging sensation, atrophy of trapezius muscle, while the other muscles are normal in strength and sensation after neck surgery. The function of trapezius and sternocleidomastoid muscles is abnormal on electromyography.
(2) Diagnosis of parasympathetic craniofacial area and brainstem nuclear injury The parasympathetic nerve damage caused by craniofacial fracture, craniofacial tumors or other lesions is extremely rare, and the posterior group of cerebral nerves on one side is often involved at the same time, and other signs of cerebral nerve damage can be combined according to the location and nature of the lesion, and the parasympathetic nerve damage caused by the brainstem lesion is often accompanied with medullary paralysis. imaging examinations such as CT and MRI can help to diagnose the primary disease. Imaging examinations such as CT and MRI are helpful for the diagnosis of the primary disease.
2.Diagnosis of combined injury
In diagnosis, it should be clarified whether it is a simple injury of the parasympathetic nerve or a combined injury of other cerebral nerves. If it occurs together with the damage to the posterior cerebral nerves and other cerebral nerves, it may be manifested as:
(1) Avellis syndrome: damage to the vagus nerve and the medial branch of the parasympathetic nerve.
(2) Jackson syndrome: Damage to the vagus, parasympathetic, and hypoglossal nerves.
(3) Schmidt’s syndrome: vagal and parasympathetic damage.
(4) Collet-Sicard syndrome Paralysis of the glossopharyngeal, vagus, parasympathetic, and hypoglossal nerves.
(5) Jugular foramen syndrome (Vernet syndrome) Paralysis of the glossopharyngeal, vagus, and parasympathetic nerves.
(6) Others: Pontocerebellar horn syndrome, foramen magnum occipitalis syndrome, lateralized skull base syndrome (Garcin syndrome or Guillain-Garcin syndrome, complete or incomplete).
3. Etiologic diagnosis
Search for the cause of parasympathetic nerve injury.
Treatment
1. Treatment of parasympathetic spinal cord injury caused by cervical surgery
(1) Timing of surgery Most scholars believe that after parasympathetic nerve injury, it should be observed and treated conservatively for 1~2 months, and if there is a sign of recovery of nerve function, it can be treated conservatively, if there is no sign of recovery, then it should be treated surgically. Some scholars also believe that surgery-induced parasympathetic nerve injuries are mostly cut or ligated injuries, which should not be observed conservatively and should be explored by surgery as early as possible once the diagnosis is confirmed.
(2) Surgical method The patient lies flat, head turned to the healthy side, shoulders slightly elevated. Epidural anesthesia. With the operation site as the center, make an oblique incision between sternocleidomastoid muscle and trapezius muscle, 8-10 cm long, cut the skin and cervical vastus muscle, one side of the posterior edge of the sternocleidomastoid muscle, pay attention to the cervicocervical cutaneous nerve not to be injured, and the other side of the anterior edge of the trapezius muscle to be separated. The parasympathetic nerve is located in the posterior cervical triangle, and after it passes out at the midpoint of the posterior border of the sternocleidomastoid muscle, it travels diagonally downward along the surface of the scapularis muscle, crosses the posterior cervical triangle to the anterior border of the trapezius muscle, and then passes into this muscle.
(3) Surgical effect The parasympathetic nerve is a pure motor nerve, and the injury site of the posterior cervical triangle is close to the endings, therefore, surgical release or anastomosis, most of the efficacy of the treatment is more satisfactory, and the recovery is faster. Even advanced parasympathetic nerve injuries should be actively treated surgically. The main factors affecting the outcome of surgery are the severity of nerve injury and the timing of surgery after injury. Surgery for partial nerve injury is better than that for complete nerve injury. Surgery within a few months after injury is better, while surgery for more than one year is worse.
2.Treatment of parasympathetic nerve injury caused by other reasons
Most of the treatments for parasympathetic nerve injury caused by skull base fracture utilize neurotrophic drugs and vasodilators as the main conservative treatment, together with physiotherapy and acupuncture. For the damage of the parasympathetic nerves caused by lesions of the skull base such as tumors and malformations of the occipital foramen magnum, first of all, the primary disease should be treated actively, and then the relevant nerves should be identified carefully under the operating microscope, and then the nerves should be preserved as much as possible from the anatomical and functional aspects, so as to avoid surgical malpractice and roughness of operation, which will further aggravate the damage of the nerve by excessively pulling the nerves or injuring the nerve arteries supplying the blood. Neurotrophic and vasodilator agents should be given after surgery to promote the recovery of nerve function.
Prognosis
In paraneoplastic nerve injury caused by various reasons, if the cause of the disease can be relieved and the dissected nerve can be reconstructed, the paraneoplastic nerve function can be restored to a certain extent. It is especially meaningful to reconstruct the parasympathetic nerves occurring in the spinal cord.