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Spastic (flaccid paresis) of the lower extremities: causes, symptoms, diagnosis, treatment
Last reviewed: 23.04.2024
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Symmetrical predominantly distal weakness (spastic or flaccid paresis) of the lower limbs
This particular category of patients with distal weakness in the legs. As a rule, such diseases lead to dysbasia. It is always useful to remember that among the causes of distal lower paraparesis is known not only polyneuropathy, but also processes at the muscular, spinal and even cerebral levels.
[The main causes of spastic (flaccid paresis) of the lower extremities:
- Parasagital tumor or (rarely) cortical atrophic process.
- Spinal cord lesions (extramedullary and intramedullary).
- Progressive spinal muscular atrophy.
- Amyotrophic lateral sclerosis (lumbosacral form).
- Defeats cone of the spinal cord and ponytail.
- Hereditary motor-sensory polyneuropathy type I and II (amyotrophy Sharko-Mari-Tuta).
- Myopathy.
- Polyneuropathy.
- Bilateral lesion of the peroneal nerve.
Medial lesion of the cerebral hemispheres.
Processes involving the precentral gyrus from both sides can cause a spastic, predominantly inferior distal paraparesis. Etiology is similar to that described in the syndrome of lower spastic paraparesis.
Lesions of the spinal cord.
Such a process causes predominantly distal spastic paraparesis only when there is a bilateral bilateral extramedullary lesion of the spinal cord involving the corticospinal tract, and in particular the surface fibers leading to the lower extremities. The intramedullary process (tumor or syringomyelia) in the lower lumbar region or the upper sacral region of the spinal cord can affect the anterior horn cells involved in the innervation of the muscles of the lower extremities (leading to a slowly progressing flaccid paralysis, always accompanied by loss of sensitivity, often with micturition). Such lesions are specified in MRI, lumbar puncture and myelography.
Progressive spinal amyotrophy.
With spinal muscular atrophy, distal leg muscles are rarely involved first, but if involved, it is often symmetrical. The diagnosis is confirmed by EMG-study, indicating the neuronal level of lesion with unchanged rates of excitation along the nerves.
Lumbosacral form of amyotrophic lateral sclerosis.
This form of amyotrophic lateral sclerosis begins with asymmetric weakness and atrophy of the distal parts of the legs (more often starts with one leg, then the second one is involved), fascicular twitching in them, then an ascending flow with diffuse EMG signs of anterior hypertension and attachment of symptoms of upper motoneuron failure.
Defeat of the cone and the "horse tail".
Such damage, causing a bilateral distal flaccid leg paresis, is always accompanied by severe sensory impairment and urinary disorders.
Hereditary motor-sensory polyneuropathy of types I and II (amyotrophy of Charcot-Marie-Toot).
Variants of amyotrophy of Charcot-Marie-Toot are manifested exclusively by bilateral, distal atrophies of the leg muscles with paralysis or paresis of the feet (familial disease, very slow progresses, high arch of the foot, absence of achilles reflexes, well developed thigh muscles ("stork legs", "inverted bottle ") The muscles of the hands are involved later, the vibration sensitivity may be distally broken in the lower limbs, while in type I the rate of excitation along the nerve can be significantly reduced.
Myopathy.
In rare cases, myopathy leads to a symmetrical distal or predominantly distal weakness; among the variants - myotonic dystrophy of Steinert-Butten and congenital distal myopathy of Welander (and Beimonda). Such syndromes lead to a purely motor deficiency and often involve upper limbs.
Polyneuropathy.
In most polyneuropathies of various origins, weakness both at the beginning of the disease and later is usually distal, often accompanied by paresthesia, subjective sensitivity disorder, hanging feet and "steppe," the absence of achilles reflexes, characteristic changes in EMG.
Two-sided symmetrical lesion of the peroneal nerve.
Such damage due to mechanical compression (found in unconscious patients and other risk factors) leads to bilateral involvement of the muscles of the solely anterior tibial area, paralysis of the peroneal muscles (without the involvement of gastrocnemius muscles, with the preservation of achilles reflexes), loss of sensitivity on the rear of the foot and the lateral surface of the shin.
Diagnostic studies with distal weakness in the legs:
General and biochemical blood test; Analysis of urine; EMG; a study of the rate of excitation on the peripheral nerves; muscle biopsy; CT or MRI of the brain and spinal cord; investigation of cerebrospinal fluid.