Funicular myelosis is a lesion of the spinal cord that develops due to vitamin B12 deficiency. As a rule, it is combined with pernicious anemia. It is manifested by a disorder of deep sensitivity, motor disorders in the form of sluggish lower paralysis with pyramidal signs, deviations in the mental sphere. Funicular myelosis is diagnosed by determining the level of B12 in the blood, conducting neurological, hematological and gastroenterological examinations. Treatment consists in replenishing vitamin B12 deficiency, observing a diet rich in vitamin B12, and introducing other vitamins of group B. The prognosis is favorable.
General information
Funicular myelosis develops due to degenerative processes occurring in the posterior and lateral spinal cords against the background of vitamin deficiency B12 (cyanocobalamin deficiency). Since B12 deficiency also leads to malignant pernicious anemia, it almost always accompanies funicular myelosis. The first description of this combined pathology was given by Lichtheim in 1887 .
Funicular myelosis can develop at any age, but more often (about 90% of cases) occurs after the age of 40. The cause of the disease can be both exogenous vitamin deficiency B12, i.e. insufficient intake of cyanocobalamin from food, and endogenous vitamin deficiency B12, due to malabsorption in various gastrointestinal pathologies. In addition, in more than 50% of cases, funicular myelosis is accompanied by the formation of antibodies to the internal Castle factor and the formation of atrophic gastritis, which indicates existing immune disorders. In connection with the above, funicular myelosis is in the circle of interests of several clinical disciplines: neurology, gastroenterology, immunology.
Causes
Exogenous vitamin deficiency B12 occurs with anorexia, complete exclusion from the diet of cyanocobalamin-rich meat, fish and dairy products, prolonged fasting or malnutrition, leading to alimentary dystrophy. Endogenous vitamin deficiency B12 is associated with impaired absorption of cyanocobalamin. For successful absorption, the transformation of vitamin B12 into its digestible form is necessary, which is carried out thanks to the gastromucoprotein synthesized by the stomach — the internal Castle factor. The synthesis of the latter is significantly reduced with achilia, gastric tumors, gastric resection or gastrectomy, which leads to impaired absorption of cyanocobalamin. This is the most common cause of funicular myelosis.
Various intestinal diseases accompanied by malabsorption syndrome may also be the cause of insufficient absorption of B12. These include: Crohn’s disease, tuberculous enteritis, sprue, celiac disease, Whipple’s disease, Pellagra, postresection syndrome of the short intestine, etc. The reduced intake of cyanocobalamin into the body is due to its excessive absorption by the intestinal flora, an excess of which is observed during the formation of a stagnant “blind” loop of the intestine after the formation of enteroanastomosis, with intestinal diverticulosis and diphyllobothriosis.
The pathogenesis of pathological changes in the spinal cord that determine funicular myelosis has not been fully established. The main one is considered to be the dysfunction of methionine synthase and methylmalonyl-CoA-mutase — enzymes involved in the formation of myelin and the formation of the myelin sheath of nerve fibers. Morphologically, funicular myelosis is accompanied by demyelination of fibers passing in the posterior and lateral spinal columns. Moreover, the process of demyelination is most pronounced in the back pillars, where the paths of deep sensitivity (the paths of Gaulle and Burdach) pass. In the lateral pillars, foci of demyelination affect the pathways of motor activity (pyramidal, spinal, spinothalamic, etc.). In some cases, demyelination of the optic nerve fibers is noted.
Symptoms
The clinical picture consists of sensory-motor disorders and mental disorders. The disease debuts with the appearance of paresthesia and general weakness of Paresthesia in the form of tingling, transient numbness, crawling goosebumps, heat occur in the fingers of the extremities, then cover the shoulders, chest and abdomen. Muscle-joint sensitivity is affected, then vibration sensitivity. As a result, sensitive ataxia develops, accompanied by discoordination of movements, instability, shaky gait. Then there is weakness in the limbs, mainly in the legs (lower paraparesis). Initially, paresis is spastic in nature with increased tendon reflexes, muscle hypertension, foot clonus. Then muscle tone decreases, reflexes fade. Paresis acquires peripheral features. However, pathological foot reflexes remain, indicating the defeat of the pyramidal pathway. Over time, the patient loses the ability to walk. Pelvic disorders (encopresis, urinary incontinence, impotence) are added.
Mental disorders have a variable nature. Depression, apathy, irritability, hypersomnia, and sometimes acute psychosis are possible. In some cases, optic neuropathy develops, manifesting a progressive decrease in visual acuity with loss of the central part of the visual field (central scotoma). Along with neurological and ophthalmological manifestations, funicular myelosis is accompanied by symptoms of pernicious anemia: pallor, crimson tongue color, glossitis and/or stomatitis, tachycardia, shortness of breath, etc.
Diagnostics
The combination of neurological symptoms with manifestations of anemia immediately raises suspicion of the existence of cyanocobalamin deficiency. In order to confirm this assumption, an analysis of the content of B12 in the blood is carried out. Further diagnosis is carried out by a neurologist together with a gastroenterologist and a hematologist. To confirm the diagnosis and establish the cause of beriberi, it is necessary: a clinical blood test, a study of the secretory function of the stomach (gastroscopy, gastric probing, analysis of gastric juice), an analysis for antibodies to the internal factor of Castle, an examination of the intestine (overview radiography, radiography of the passage of barium).
Visualization of spinal morphological changes (foci of demyelination) is possible using MRI of the spine. It also makes it possible to differentiate funicular myelosis from compression myelopathy in spinal tumors, vertebrogenic myelopathy, spinal tumors and cysts. Lumbar puncture and examination of cerebrospinal fluid are carried out to exclude infectious myelitis and hematomyelia. If it is necessary to exclude neurosyphilis, an RPR test is prescribed. In order to diagnose hematological disorders, a sternal puncture is performed with subsequent examination of the myelogram. In case of visual disorders, an ophthalmologist’s consultation with visometry, perimetry and ophthalmoscopy is indicated.
Treatment
Therapy consists mainly in correcting cyanocobalamin deficiency. At the beginning of treatment, cyanocobalamin preparations are administered intramuscularly daily. After 5-10 days, the drug is administered once a week, after 4 weeks — once a month. If there are indications, it is possible to prescribe monthly injections of vitamin B12 for life. A diet with the use of nutrients rich in B vitamins (different varieties of fish, beef, cottage cheese, cheese, chicken eggs, crabs) is recommended. In parallel with the treatment with vitamin B12, the course administration of other drugs of this group is carried out: thiamine (B1) and pyridoxine (B6).
The presence of folic acid deficiency is an indication for its appointment. However, it is better to start treatment with folic acid after the cyanocobalamin deficiency is replenished, because otherwise it can aggravate the severity of neurological symptoms. According to the indications, the secretory function of the stomach and intestinal absorption disorders are corrected, and urogenital infection is prevented. For the fastest and most complete restoration of sensorimotor functions, massage, physiotherapy and physical therapy are performed.
As a rule, funicular myelosis has a subacute or slow course. Before determining the cause of its occurrence, the disease was fatal for 2 years. With timely vitamin B12 therapy, the prognosis is favorable. At the beginning of treatment a few months after the onset of the disease, it is possible to achieve stabilization of the condition, but one cannot count on a complete regression of neurological symptoms.