Alternating syndromes: causes, symptoms, diagnosis

The nuclei of the cranial nerves and their roots, as well as the long ascending and descending tracts, are tightly “packed” in the brainstem. Therefore, damage to the brainstem usually affects both segmental formations (cranial nerves) and long conductors, which leads to characteristic combinations of symptoms in the form of ipsilateral damage to the cranial nerve and contralateral hemisyndrome (alternating syndromes). Lesions in the brainstem are often unilateral and rarely do not involve certain nuclei of the cranial nerves, which significantly simplifies the determination of the level of damage.

The brainstem also contains such important structures as the gaze control system; the ascending reticular activating system, which ensures the level of wakefulness and consciousness of a person (oral parts of the brainstem); vestibular nuclei and conductors; the system of postural control and regulation of muscle tone; descending oculosympathetic fibers, systems for ensuring vital functions (respiration, circulation, swallowing). The ventricular system of the brain is also located here (partially).

Brain stem lesions manifest themselves not only as alternating syndromes, but also as many other syndromes: pupillary and oculomotor disorders, various gaze disorders (combined vertical gaze palsy, upward gaze palsy, downward gaze palsy, internuclear ophthalmoplegia, horizontal gaze palsy, global gaze palsy, one-and-a-half syndrome), disturbances of consciousness and wakefulness (hypersomnic and comatose states); "posterior" syndrome of akinetic mutism; "locked-in" syndrome; cerebellopontine angle syndrome; bulbar and pseudobulbar syndrome; brainstem vestibular symptom complex; tectal deafness syndrome; respiratory distress syndromes (in a patient in a coma); sleep apnea syndrome; Hyperkinetic syndromes of brainstem origin (facial myokymia, opsoclonus, velopalatine myoclonus, startle syndromes); acute insufficiency of postural control (drop attacks); brainstem nystagmus syndromes; brainstem compression syndromes with compression of the temporal lobe in the tentorium or foramen magnum); Bruns syndrome; obstructive hydrocephalus (for example, with compression of the Sylvian aqueduct) with corresponding clinical manifestations; dysgenesia syndromes (Arnold-Chiari syndrome; Dandy-Walker syndrome); foramen magnum syndrome.

Next, we will focus primarily on those brainstem syndromes that were little covered in the previous sections of the book, namely, the syndromes most typical of ischemic stroke in the brainstem.

A. Medulla oblongata injury syndromes:

• I. Medial medullary syndrome.
• II. Lateral medullary syndrome.
• III. Combined syndrome (medial and lateral) syndrome or hemimedullary syndrome.
• IV. Lateral pontomedullary syndrome.

B. Syndromes of damage to the pons:

• I. Ventral pontine syndromes
• II. Dorsal pontine syndromes.
• III. Paramedian pontine syndrome.
• IV. Lateral pontine syndromes.

C. Syndrome of universal dissociated anesthesia.

D. Syndromes of mesencephalon damage:

• I. Ventral syndrome of the root of the third cranial nerve.
• II. Dorsal syndrome of the root of the third cranial nerve.
• III. Dorsal mesencephalic syndrome.
• IV. Superior basilar syndrome.

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A. Medulla oblongata damage syndromes

Injuries to the conductors at this level of the brainstem may result in monoplegia, hemiplegia, alternating hemiplegia, and a variety of sensory disturbances. Lower paraplegia or decerebrate rigidity may occur. Involvement or compression of the efferent fibers from both nuclei of the vagus nerve may lead to profound disturbances of cardiac and respiratory function, arterial pressure, and death.

Damage to the medulla oblongata may be acute, subacute or chronic and have a variety of etiologies. These may include tumors, tuberculoma, sarcoidosis, vascular damage (hemorrhages, thrombosis, embolism, aneurysms, malformations), polioencephalitis, poliomyelitis, multiple sclerosis, syringobulbia, progressive bulbar palsy (ALS), congenital anomalies, infectious, toxic and degenerative processes. Extramedullary syndromes may be caused by trauma, fractures of the bones of the base of the skull, skeletal developmental disorders, acute and chronic inflammation of the membranes and sudden increase in intracranial pressure, leading to infringement of the medulla oblongata in the foramen magnum. A cerebellar tumor may lead to a similar picture.

I. Medial medullary syndrome (anterior bulbar syndrome of Dejerine)

1. Ipsilateral paresis, atrophy and fibrillation of the tongue (caused by damage to the 12th nerve). Deviation of the tongue towards the lesion. Rarely, the function of the 12th nerve may be preserved.
2. Contralateral hemiplegia (due to pyramidal involvement) with preserved facial muscle functions.
3. Contralateral decrease in muscle-articular and vibration sensitivity (caused by involvement of the medial lemniscus). Since the spinothalamic tract, located more dorsolaterally, remains uninvolved, pain and temperature sensitivity are preserved.

If the lesion extends dorsally, affecting the medial longitudinal fasciculus, an upward-beating nystagmus may occur. Sometimes the medial medullary syndrome develops bilaterally, leading to quadriplegia (with preserved functions of the VII nerve), bilateral lingual plegia, and decreased muscle-articular and vibration sensitivity in all four limbs.

The syndrome is caused by occlusion of the anterior spinal artery or vertebral artery. The anterior spinal artery supplies the ipsilateral pyramid, medial lemniscus, and the 12th nerve with its nucleus.

Involvement of the anterior spinal artery or trauma may occasionally result in crossed hemiplegia (decussation syndrome) with contralateral spastic paresis of the leg and ipsilateral spastic paresis of the arm. There is also flaccid paresis and atrophy of the ipsilateral sternocleidomastoid and trapezius muscles and, occasionally, the ipsilateral half of the tongue. More extensive lesions above the decussation may result in spastic tetraplegia.

A variant of medial medullary syndrome is Avellis syndrome.

Medial medullary infarction is difficult to diagnose without MRI.

II. Lateral medullary Wallenberg syndrome (Wallenberg) - Zakharchenko.

1. Ipsilateral decreased pain and temperature sensitivity in the face (due to involvement of the nucleus tractus spinalis digemini). Sometimes ipsilateral facial pain is observed.
2. Contralateral decrease in pain and temperature sensitivity in the trunk and limbs due to damage to the spinothalamic tract.
3. Ipsilateral paralysis of the soft palate, pharynx and vocal cord with dysphagia and dysarthria due to involvement of the nucleus ambiguus.
4. Ipsilateral Horner's syndrome (due to involvement of descending sympathetic fibers).
5. Dizziness, nausea and vomiting (due to involvement of the vestibular nuclei).
6. Ipsilateral cerebellar signs (due to involvement of the inferior cerebellar peduncle and partially the cerebellum itself).
7. Sometimes hiccups and diplopia (the latter is observed in case of involvement of the lower parts of the pons).

The syndrome is caused by damage to the lateral medullary area and inferior cerebellum. It most often develops with occlusion of the intracranial portion of the vertebral artery or the posterior inferior cerebellar artery. Other causes: spontaneous dissection of the vertebral artery, cocaine abuse, medullary tumors (usually metastases), abscesses, demyelinating diseases, radiation damage, hematoma (due to rupture of a vascular malformation), manipulation during manual therapy, trauma.

In this syndrome, various disturbances of eye movements and vision have also been described: oblique deviation (caused by the elevation of the contralateral eyeball), ipsilateral head tilt with torsion of the eyeballs (ocular tilt reaction) with complaints of double vision or tilt of visible surrounding objects, various types of nystagmus, “eyelid nystagmus” and other ocular phenomena.

Some researchers include the Sestan-Chenais syndrome and the Babinski-Nageotte syndrome in the form of a combined medial and lateral infarction among the variants of this syndrome.

At the same time, such symptom complexes as Jackson syndrome and Schmidt syndrome (as well as Tapia, Berne, Villaret, Collet-Sicard and other syndromes) are classified primarily as “neural” syndromes (syndromes of cranial nerve damage), in which involvement of brain matter is rarely observed.

As for the alternating Avellis syndrome, which is manifested by damage to the X pair (ipsilateral paralysis of the soft palate and vocal cord), as well as the spinothalamic tract and descending oculosympathetic fibers (contralateral hemianesthesia and ipsilateral Horner's syndrome), it apparently belongs to such rarities that it has recently ceased to be mentioned in neurological monographs and manuals.

III. Hemimedullary syndrome.

Rarely, a combined syndrome (medial and lateral medullary syndromes (hemimedullary syndrome) may be observed, usually caused by occlusion of the intracranial vertebral artery.

In general, the clinical picture of medullary infarctions is very heterogeneous and depends on the extent of ischemia in the medulla oblongata; sometimes they extend to the lower parts of the pons, the upper parts of the spinal cord and the cerebellum. In addition, they can be unilateral or bilateral.

Damage to the caudal parts of the brainstem can lead to neurogenic pulmonary edema.

IV. Lateral pontomedullary syndrome.

In this case, the clinical picture of lateral medullary syndrome is observed plus several pontine symptoms, including:

Ipsilateral weakness of facial muscles (due to involvement of the VII nerve)

Ipsilateral tinnitus and sometimes hearing loss (due to involvement of the VIII nerve).

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B. Syndromes of damage to the pons (pontine syndromes).

I. Ventral pontine syndromes.

1. Millard-Gubler syndrome is caused by a lesion in the lower part of the pons (usually an infarction or tumor). Ipsilateral peripheral paresis of the facial muscles (VII cranial nerve). Contralateral hemiplegia.
2. Raymond syndrome is caused by the same processes. Ipsilateral paresis of the rectus lateralis muscle (VI cranial nerve). Paresis of gaze toward the lesion. Contralateral hemiplegia due to involvement of the pyramidal tract.
3. "Pure" (motor) hemiparesis. Localized lesions in the region of the base of the pons (especially lacunar infarcts) that involve the corticospinal tract can cause pure motor hemiparesis. (Other locations of lesions that can cause this pattern include the posterior limb of the internal capsule, the cerebral peduncles, and the medullary pyramids.)
4. Dysarthria and clumsy hand syndrome.

Local lesions at the base of the bridge (especially lacunar infarctions) at the border of the upper third and lower two-thirds of the bridge can cause this syndrome. In this syndrome, weakness of the facial muscles and severe dysarthria and dysphagia develop together with paresis of the arm, on the side of which there may be hyperreflexia and Babinski's sign (with preserved sensitivity).

(A similar picture can be observed with damage to the knee of the internal capsule or with small deep hemorrhages in the cerebellum).

5. Ataxic hemiparesis.

Local damage at the base of the bridge (most often lacunar infarctions) of the same localization can lead to contralateral hemiataxia and paresis of the leg (sometimes dysarthria, nystagmus and paresthesia are detected) on the same side of the body.

(This syndrome has also been described in thalamocapsular lesions, processes in the area of the posterior limb of the internal capsule, the red nucleus, and in superficial infarctions in the paracentral region.)

6. Locked-in syndrome.

Bilateral damage to the ventral pons (infarction, tumor, hemorrhage, trauma, central pontine myelinolysis, less commonly other causes) can lead to the development of this syndrome (de-efferentation state). Clinical manifestations include the following:

Quadriplegia due to bilateral involvement of the corticospinal tracts at the base of the pons. Aphonia due to involvement of the corticobulbar fibers going to the nuclei of the lower cranial nerves. Sometimes there is a disturbance of horizontal eye movements due to involvement of the roots of the sixth cranial nerve. Since the reticular formation of the brainstem is not damaged in this syndrome, patients are awake. Vertical eye movements and blinking are intact.

The state of deeffectoration is also observed in purely peripheral lesions (poliomyelitis, polyneuropathy, myasthenia).

II. Dorsal pontine syndromes

Foville syndrome is caused by damage to the dorsal parts of the tegmentum of the caudal third of the pons: Contralateral hemiplegia (hemiparesis).

Ipsilateral peripheral facial palsy (VII nerve root and/or nucleus). Inability to move the eyes ipsilaterally in concert due to involvement of the paramedian pontine reticular formation or VI (abducens) nerve nucleus, or both.

Raymond-Cestan syndrome is observed with rostral lesions of the dorsal parts of the pons. This syndrome is characterized by:

Cerebellar ataxia with coarse "rubral" tremor due to involvement of the superior cerebellar peduncle.

Contralateral decrease in all types of sensitivity due to involvement of the medial lemniscus and spinothalamic tract.

With ventral extension of the lesion, contralateral hemiparesis (involvement of the corticospinal tract) or gaze palsy toward the lesion (involvement of the paramedian reticular formation of the pons) may occur.

III. Paramedian pontine syndrome

Paramedian pontine syndrome can be represented by several clinical syndromes:

• Unilateral medio-basal infarction: severe facio-brachiocrural hemiparesis, dysarthria and homolateral or bilateral ataxia.
• Unilateral mediolateral basal infarction: mild hemiparesis with ataxia and dysarthria, ataxic hemiparesis or dysarthria-clumsy hand syndrome.
• Unilateral medio-central or medio-tegmental infarction: dysarthria-clumsy hand syndrome; ataxic hemiparesis with sensory or eye movement disturbances; hemiparesis with contralateral paralysis of the facial muscles or m. rectus lateralis (VII or VI nerves).
• Bilateral centro-basal infarction: These patients develop pseudobulbar palsy and bilateral sensorimotor impairment.

The most common causes of paramedian pontine infarctions are lacunar infarctions, vertebrobasilar insufficiency with infarctions, and cardiogenic embolism.

IV. Lateral pontine syndromes

Marie-Foix syndrome occurs with lateral damage to the pons, especially if the middle cerebellar peduncles are affected, and includes:

Ipsilateral cerebellar ataxia due to involvement of connections with the cerebellum. Contralateral hemiparesis (involvement of the corticospinal tract).

Variable contralateral hemihypesthesia of pain and temperature sensitivity due to involvement of the spinothalamic tract.

C. Syndrome of universal dissociated anesthesia

Universal dissociative anesthesia is a rare syndrome described in patients with combined occlusion of the right superior cerebellar artery and the left posterior inferior cerebellar artery. The first artery lesion leads to lateral superior pontine infarction, the second artery lesion leads to left-sided lateral medullary Wallenberg-Zakharchenko syndrome. The patient has decreased pain and temperature sensitivity on the face, neck, trunk and all extremities, while tactile, vibration and muscle-joint sensitivity are preserved (dissociated decreased sensitivity).

Hemorrhagic injuries of the pons are accompanied by impaired consciousness, coma and have a slightly different clinical picture.

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D. Syndromes of mesencephalon damage

I. Ventral syndrome of the root of the third cranial nerve Weber.

Lesions in the cerebral peduncle affecting the fibers of the pyramidal tract and the root of the III nerve manifest as follows: Contralateral hemiplegia. Ipsilateral paralysis of the muscles innervated by the III nerve.

II. Dorsal syndrome of the root of the third cranial nerve of Benedict (Benedikt)

Caused by damage to the mesencephalon tegmentum with involvement of the red nucleus, superior cerebellar peduncles and the root of the third cranial nerve:

Ipsilateral paralysis of muscles innervated by the third nerve.

Contralateral involuntary movements, including intention tremor, hemichorea, hemiballismus, due to involvement of the red nucleus.

Similar clinical manifestations develop with more dorsal damage to the midbrain tegmentum, which affects the dorsal parts of the red nucleus and the superior cerebellar peduncles and is called Claude syndrome, in which cerebellar symptoms (contralateral hemiataxia, hypotonia) predominate and there is no hemiballismus.

III. Dorsal mesencephalic syndrome

It manifests itself mainly by neuro-ophthalmological phenomena. Dorsal mesencephalic syndrome (Sylvian aqueduct syndrome or Parinaud syndrome) is most often detected against the background of hydrocephalus or a tumor of the pituitary region and includes all (or some of) the following signs:

1. Paralysis of upward (sometimes downward) gaze.
2. Pupillary abnormalities (usually dilated pupils with dissociation of the reaction to light and to accommodation with convergence).
3. Converging and retractor nystagmus when looking up.
4. Pathological eyelid retraction.
5. Eyelid lag.

IV. Superior basilar syndrome

Caused by occlusion of the rostral portions of the basilar artery (usually due to embolism), resulting in infarction of the midbrain, thalamus, and part of the temporal and occipital lobes. The syndrome has also been described in patients with giant aneurysms of this portion of the basilar artery, with vasculitis of the artery, and after cerebral angiography. Variable manifestations of this syndrome include:

1. Eye movement disorders (unilateral or bilateral upward or downward gaze palsy, convergence disorders, pseudo-abducens palsy, convergence and retractor nystagmus, eye abduction disorders, upper eyelid lag and retraction, oblique deviation).
2. Pupillary disorders.
3. Behavioral disorders (hypersomnia, peduncular hallucinosis, memory impairment, delirium).
4. Visual impairment (hemianopsia, cortical blindness, Balint syndrome).
5. Motor and sensory deficits.

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