What Is Lateral Medullary Syndrome?

Dorsal medullary infarction caused by posterior inferior cerebellar artery occlusion, called dorsal lateral medullary syndrome, also known as posterior inferior cerebellar artery syndrome or Wallenberg syndrome, is the most common type of brain stem infarction. The elderly are mostly caused by thrombosis, while the young and middle-aged are mostly caused by cardiogenic or arterial embolism. In fact, most of this syndrome is not caused by occlusion of the posterior inferior cerebellar artery, but caused by occlusion of the vertebral artery near the inferior cerebellar artery.

Lateral medullary syndrome

Basic concepts of lateral bulbar syndrome

Dorsal medullary infarction caused by posterior inferior cerebellar artery occlusion, called dorsal lateral medullary syndrome, also known as posterior inferior cerebellar artery syndrome or Wallenberg syndrome, is the most common type of brainstem infarction. The elderly are mostly caused by thrombosis, while the young and middle-aged are mostly caused by cardiogenic or arterial embolism. In fact, most of this syndrome is not caused by occlusion of the posterior inferior cerebellar artery, but caused by occlusion of the vertebral artery near the inferior cerebellar artery.

Clinical manifestations of lateral bulbar syndrome

The posterior inferior cerebellar artery emerges from the upper part of the vertebral artery and is the largest and most variably branch of the vertebral artery. It mainly supplies the mid-upper lateral region of the medulla, the bottom of the cerebellar hemisphere and the posterior part below the vermiform. After the posterior inferior cerebellar artery is branched from the outer side of the vertebral artery, it travels backward and up to the bottom of the cerebellum when it is inward and lateral. The inner branch is anastomized with the contralateral posterior inferior cerebellar artery and the ipsilateral superior cerebellar artery, and the lateral branch is anastomosis with the ipsilateral inferior cerebellar artery. The small branch artery supplying the lateral part of the medulla oblongata from the trunk of the posterior inferior cerebellum is the terminal artery. Therefore, when the posterior inferior cerebellar artery is occluded, only the infarction to the small branch blood supply area of the medullary bulb, that is, the dorsal lateral oblongata infarct.

Anatomy of the dorsal lateral medulla and its signs of damage:

Nerve spinal tract, trigeminal spinal nucleus and spinal thalamus tract: After the injury, the diseased side and contralateral torso and limb (excluding the face) pain, temperature sensory disorder, that is, cross sensory disorder;

Suspected nucleus: soft palate paralysis, articulation, and swallowing disorder of the affected side occur, and the pharynx is weakened or lost;

Subventricular nucleus: showing dizziness, nausea, vomiting, and nystagmus after involvement;

Sympathetic descending fibers of the reticular structure: when damaged, it shows the Horner's sign of incomplete lesion side, which is mainly manifested by small pupils and / or slight drooping of eyelids;

Anterior and posterior spinal cerebellar tracts and trochoids: after the injury, ipsilateral limbs and trunk ataxia appear.

The typical dorsal lateral medulla syndrome can be manifested by the above five symptoms.

Clinical classification of lateral bulbar syndrome

Because there are many anatomical variations of the posterior inferior cerebellar artery, for example, only a single posterior inferior cerebellar artery is separated by the basal artery; it is separated from the vertebral artery or basilar artery by a trunk together with the anterior inferior cerebellar artery; Blood supply; the branch of the medullary branch of the posterior inferior cerebellum sends small branches to the facial and auditory nerves, which complicates clinical symptoms. This syndrome may appear atypical clinical manifestations. According to observations at home and abroad, only the performance of sensory disorders is divided into 8 types, which are as follows:

1. Type cross sensory disorder, which is a typical manifestation. It is the manifestation of lesions of the trigeminal spinal tract or nucleus of the lesion and the thalamus of the spinal cord.

2. Type lesions have side-to-side and half-body pain and temperature dysfunction. It is caused by damage to the secondary trigeminal nerve fibers (trigeminal system) on the lesion side and the thalamus tract of the spinal cord.

3. Type bilateral and lateral contraceptive lesions. It is a manifestation of the involvement of the spinal tract of the trigeminal nerve and its secondary fibers and the thalamus of the spinal cord at the lesion side.

4. Type lesions of the contralateral half of the body (except the face) sensory disorders. It is caused by damage to the thalamus tract of the spinal cord at the focus side.

5. Type V only has sensory dysfunction on the lateral side of the lesion, and sometimes only the first, second or first two branches of the trigeminal nerve. It is the spinal tract of the trigeminal nerve involved in the lesion.

6. Type VI bilateral sensory disturbance. It is the lesion of the trigeminal spinal tract and the secondary fibers of the trigeminal nerve.

7. type only lesions on the lateral side of the sensory disturbance, the secondary trigeminal nerve involvement of the lesion.

8. -type bilateral half-body (excluding face) sensory disturbance. It is caused by lesions that affect bilateral spinal thalamus or vascular anatomy.

In addition, there are a variety of atypical manifestations such as bilateral diaphragmatic, pharyngeal, and laryngeal muscle palsy, with facial nerve palsy and / or hearing impairment, and positive pyramidal tract signs. Atypical clinical manifestations of this syndrome are mostly vertebral artery occlusion rather than posterior cerebellar inferior artery occlusion.

This syndrome is generally free of cerebellar syndrome, but it can also occur in a small number of patients. For example, Masson et al. Observed 3 patients with sudden vertigo, whose signs were similar to acute labyrinthosis, but no nystagmus, MRI showed infarction on one side of the cerebellum, and angiography of the middle segment of the lower cerebellar artery was occluded.

Recent studies have shown that this syndrome can still have complex eye movement disorders: oblique deflection of the eyeball. That is, the side eyes of the lesion turn downward and inward and the contralateral eyes turn outward. This is because people maintain resting and dynamic body balance through the vestibular organs and vestibular system. The fibers from the oval capsule are mainly projected to the ipsilateral lateral vestibular nucleus, the spherical capsule is mainly projected to the inferior vestibular nucleus, and the semicircular canal is mainly projected to the superior vestibular, medial, and inferior nucleus. Fibers are sent from the vestibular nucleus to the medial longitudinal bundle and vestibular spinal cord to regulate eyeball position and cervical muscle activity. If the above pathways are damaged, the vestibular input may be imbalanced and appear.

Oblique angular deviation. Nystagmus: It is common in this syndrome, and it can be horizontal, rotational, horizontal-rotating or horizontal-rotating-vertical. Horizontal-rotating is the most common. A small number of patients can also see a seesaw-like nystagmus, or eyelid-nystagmus (which can be induced when watching). Persistent Gaze Disorder: It is manifested that patients often feel that the body is pulled to one side, and only to the other side can they compete with it. This is due to the effects of persistent impaired gaze function, and the eyeball is easily pulled towards the lesion side.

Although the clinical manifestations of the posterior inferior cerebellar arterial syndrome are diverse, they can never be separated. As long as the basic symptoms of the syndrome are grasped, the diagnosis should not be difficult. Wang Xinde believes that the diagnosis of dorsal lateral medulla syndrome must have the following two items: suggesting that the lesion is in the medulla, that is, there must be one of dysarthria and dysphagia; suggesting that the damage is on the lateral side of the dorsal, that is, pain and temperature disorders, and limb ataxia Imbalance and Horner sign must have one.