Distinctive features of the peripheral and central paralysis

Table 3

Weakness of the upper limb muscles is more expressed than Weakness the lower limb muscles. The distal muscle groups suffer more both in the upper and the lower limbs. Paralysis (paresis) is formed on the side opposite to the focus. The line between the paralyzed and healthy sides goes along the midline of the body. This syndrome is called hemiplegia (from the Greek. Hemi-half, plege - lesion). Due to the central neuron lesions, there are signs of the segmental apparatus disinhibition - muscle tone is increased, deep reflexes revive, pathological and defensive reflexes take place (Babinski reflex is revealed early and regularly).

When there is disinhibition of segmental apparatus, apart from the symptoms mentioned above, pathological consensual movemets – synkinesis are observed. Pathological synkinesis are usually divided into global, coordination, simulation (contralateral).

Global synkinesis - involuntary movements of the paralyzed limbs, arising when the muscles of the healthy limbs are heavily tensed and for a relatively long time (e.g, under forced contraction of the fingers of the healthy hand in a fist) as well as when coughing, sneezing, laughing, crying, making effort. The nature of the global synkinesis is usually determined by selective increase in tone in the paralyzed limbs. On the upper limbs synkinesis is revealed by the flexion of the fingers, flexion and pronation of forearm, shoulder abduction (shortening synergy); on the lower limbs – by adduction of the femur, straightening in the knee joint, flexion of the foot, flexion of the fingers (extension synergy).

Coordination synkinesis - involuntary contractions of the paretic muscles, when trying to contract other, functionally connected with them muscles. Usually it takes place during the recovery of voluntary movements, when one can make some voluntary movements, but can’t keep synkinesis.

Synkinesis in hemiparesis includes so called Strumpell tibial phenomenon. The patient in the supine position can not make the rear extension of the foot on the side of paresis, but when he flexes the lower limb in the knee joint, especially with the examiner’s opposition, the anterior tibial muscle contracts and the extension in the ankle joint takes place. Raymist symptom belongs to the same category of synkinesis in hemiplegia. The patient in the supine position cannot adduct and abduct the femur on the paralyzed side. But these movements in the paretic lower limb muscles appear, when the patient makes them with the healthy limb, especially with the examiner’s opposition.

The consensual movements in hemiplegia include the symptom of involuntary lifting of the paralyzed lower limb, when the patient is in the prone position sits down on the bed without using his hands (Babinski synkinesis).

When the patient bends forward, the lower limb on the side of hemiparesis flexes involuntarily in the knee joint (Nery phenomenon). Synkinesis in the form of involuntary flexion of the thumb with the passive straightening of the fingers II-V (Klippel – Weil phenomenon) or in the form of a fan-shaped abduction of the fingers of the paralyzed upper limb when yawning.

Imitation synkinesis - involuntary movements of one limb, imitating voluntary movements of another. Imitation synkinesis includes substitutive compensatory movements, which the patient makes with a healthy limb and simultaneously with the paretic limb. The patients with the upper limb paresis sometimes facilitate the process of movement by identical tension of the healthy upper limb.

At the early stages of ontogeny the patient’s movements are symmetrical and bilateral due to bilateral irradiation of motor impulses. Then with complete myelination of pyramidal and extrapyramidal fibers and the acquisition of individual motor experience as well, the movements with the one limb become possible. The acquisition of motor skills implies not only the ability to make necessary movements, but at the same time to suppress synkinesis impulses. With the pyramidal system lesion at the level of the cortex and basalis there is disinhibition of neural connections (in the early stage of their development) in subcortical structures and imitation synkinesis, which is pathological, takes place again. Congenital imitation synkinesis expresses itself in the propagation of the impulses through associative fibers to both hemispheres of the brain, which makes the formation of many motor skills of the upper limb difficult.

So, hemiplegia syndrome is more connected with the internal capsule lesion of one of the brain hemispheres. If pyramidal fascicle on this level is not deeply and temporarily damaged (e.g due to edema), damage of its functions are reversible. When the pyramidal fibers are destructed voluntary movements are reduced and hemiplegia is formed. In this phase, the patients learn to walk. In this case paretic lower limb step forth, making a semicircle. It’s like the movement of scythe in manual mowing - "scissor gait." Continuous change of limb posture in hemiplegia got its name after the authors - Wernicke - Mann contracture (Fig.46). When localizing the focus of the pyramidal tract from the cortex to the internal capsule (precentral gyrus, paracentral lobule, radiant crown) clinical picture depends mostly on transverse dimension of the focus. If it is extensive and covers all the area of ​​the pyramidal system, the syndrome, identical to the capsular hemiplegia, takes place. However, such dense focuses are rare.

The part of the central neurons or their axons are usually involved. Suffer only those, which are connected with the regulation of the movement of one limb or only the muscles of the head area. Isolated paralysis of the lower limb is termed as monoplegia cruralis and of the upper limb - monoplegia brachialis. Paralysis have the signs of the central neuron lesion. The lesion of the upper limb is often accompanied by the lesion of the face and tongue. We see a typical syndrome - paralysis facio - linguo - brachialis - a kind of incomplete hemiplegia. A unilateral lesion of the fibers of the pyramidal fascicle can take place below the internal capsule, within the brain stem (cerebral peduncle, the brain pons, the medulla oblongata).

In this case hemiplegia on the opposite side of the focus is being developed. One of the motor cerebral nerves for the corresponding muscles of the same name side is being involved simultaneously. Some kind of clinical syndrome takes place: cerebral nerve paralysis on the focus side and hemiplegia on the opposite side, which is called alternating hemiplegia (from Lat. alternants).

The spinal cord lesion. The above crossed pyramidal fascicle pass in the lateral cords along the full length. The peripheral motor neurons are located in the anterior horns in parallel with them. At the level of each segment the fibers for forming a synapse with the corresponding neurons move away from the pyramidal fascicles. With the break of the pyramidal fibers the pyramidal fascicles for the upper and lower limbs are damaged above the cervical intumescence (the lesion of the upper cervical segments) of the spinal cord. Paralysis of the upper and lower limbs takes place (tetraplegia). Paralysis also carries the signs of the central neuron lesion (spastic tetraplegia). What movement disorders develop under transverse spinal cord lesion on the level of the thoracic segments? The fibers of the pyramidal system are broken for both lower limbs, which leads to their paralysis. The upper limbs remain unaffected. Deep reflexes and muscle tone in the lower limbs are increased, defensive pathological reflexes take place. Cutaneous reflexes below the level of lesion are extinguished. This transverse distribution of paralysis of the limbs is called paraplegia. In this case we talk about lower paraplegia, because only the lower limbs are affected. Due to the increased muscle tone (spastic phenomena) this paraplegia is called spastic paraplegia.

With the pyramidal fascicle lesion in the lateral funiculus on the level of the upper cervical segments of the spinal cord, paralysis of the upper and lower limbs takes place on the focus side (spastic hemiplegia). Facial muscles and the tongue are not affected. This syndrome is called hemiplegia of the spinal type. Isolated lesion of the motor neurons in the spinal cord happens in poliomyelitis, tick-borne encephalitis, myeloischemia etc.

With the destruction of the anterior horn cells peripheral paralysis of the upper limbs is developed in the cervical intumescence (upper flaccid paraplegia). All through spinal cord motor neuron lesion takes place, this is revealed by paralysis of both upper and lower limbs - flaccid tetraplegia.

With the lesion of the motor neurons of the lumbosacral segments, lower paraplegia with decreased muscle tone and extinction of deep reflexes in the lower limbs takes place. A few weeks later muscle atrophy (atrophic flaccid lower paraplegia) occurs. The focus in the anterior horns of the spinal cord may be limited to one or two segments. The corresponding muscle group is affected (segmental type of paralysis or myotome paralysis). Innervation of muscles, located below and above the focus, is kept.

Now we consider the paralysis with the break of the peripheral neurons outside medullary substance. In this case the roots or peripheral nerve stems may suffer. The motor disorders distribution is important for the diagnostics. In one case, a group of affected muscles coincides by some root with innervations, in the other – with nerve (see Table 2). Erb - Duchenne paralysis serves as an example. Unilateral paralysis of the deltoid muscle of the peripheral-type (axillary nerve), of the shoulder biceps muscle and humeral muscle (muscle - cutaneous nerve) and of the brachioradialis muscle (radial nerve) takes place. It’s difficult to admit simultaneous lesion of three nerve trunks, it’s more possible to suggest the position of roots - (see Table. 2). The lesion of the spinal nerve roots can be confirmed by the sensitivity disorders distribution.

If some muscles has the signs of the peripheral type paralysis and these muscles coincide with the zone ​​of one nerve innervations, it is called neural distribution type of paralysis.

In multiple lesions of nerve trunks (polyneuritis) or some hereditary diseases of the nervous system the typical syndrome is observed flaccid tetraparesis, in which muscle weakness is more pronounced in the distal limbs. Such regularity is called distal or polyneuritic distribution of paralysis.

In hereditary muscular dystrophy, atrophy and paresis are located more in the muscles of the pelvic and shoulder girdle and in the proximal limbs as well; the distal muscles are relatively intact (myopathic type of paralysis distribution). The central neuron (dendrites and body) may undergo excessive irritation.

The accumulation of subliminal irritative impulses leads to periodically coming violent discharge in the form of a stream of impulses through the central neuronal axons. The peripheral motor neuron is instantly activated, the muscles, corresponding to the focus of irritation in the cerebral cortex are contracting convulsively. The cramps of the separate muscle group are mostly of the clonic nature. Jerky sequential flexion and extension or adduction and abduction take place in one or the other joint. The attack goes on for a few minutes and can be repeated later. The patient is conscious. These paroxysms of local cramps are called cortical or Jacksonian epilepsy. The cramps usually occur in the groups of muscles, which the patient uses more often during voluntary movements. For example, a muscle spasm of the finger I occurs more frequently than that of the finger V (large area of cortical zone for the finger I see Figure 36). The cramp, beginning in the muscles of the thumb is often spread in the following order: other fingers, the hand, all the upper limb, the face; the transition to the lower limb is possible. This corresponds to the spread of excitation in adjacent motor centers in the precentral gyrus.

In some cases, local cramps are generalized, common epileptic seizure with loss of consciousness takes place. The appearance of epileptic seizures, cortical seizures in particular, often arouses a suspicion about intracranial volume process (tumor, cyst, arachnoiditis).

There is one more type of cortical epilepsy. It is characterized by the fact that the local cramps do not occur in the form of seizures, they are kept constantly. The cramps are getting more intense, and generalized, and the patient has a general epileptic seizure. In 1894 This form of the disease was described by Russian neurologist A.Y Kozhevnikov and is called Kozhevnikov epilepsy. This syndrome often occurs in chronic tick-borne encephalitis. It’s important to say there are various types of paralysis (paresis), such as organic, reflex and functional.

Organic paralysis takes place with the changes in the central or peripheral motor neuron structure due to different reasons (injuries, vascular, neoplastic, inflammatory, degenerative and other diseases).

Types of organic paralysis: сentral, peripheral, mixed. We speak about mixed paralysis (paresis) in that case, when the signs of the peripheral (muscle atrophy, hypotension, fascicular twitching) and central motor lesion are revealed simultaneously in the muscles of one limb (recovery deep reflexes, pathological signs). Mixed paresis takes place more frequently in amyotrophic lateral sclerosis.

Reflex paresis is characterized by the deep reflexes recovery with the presence of pathological signs in sufficient preservation of muscle strength. This happens under the partial lesion of cortical-muscular or under dislocation impact on the pyramidal system in the case of the extensive pathological focus, located close to it.

Functional paralysis (paresis) is connected with the impact of the psychogenic factors, which lead to neurodynamical disorders of the central nervous system and occur mainly in hysteria. In this paralysis trophism and muscle tone do not change, deep reflexes are preserved, pathological capral and foot signs are absent.

Chapter 5

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