Tabes dorsalis is a chronic, progressive, deterioration of the parenchyma of the posterior columns of the spinal cord, and of the posterior sensory ganglia and nerve root. The condition is a form of neurosyphilis.

The neurosyphilis is caused by the organism, Treponema pallidum. Treponema pallidum is delicate, slender, and spiral. It is identified by a dark-field microscope or fluorescent techniques. The organism cannot survive for long periods outside the human body. Neurosyphilis, without symptoms, occurs prior to symptomatic neurosyphilis. It occurs in about 15% of those originally diagnosed with latent syphilis, in 12% of those with cardiovascular syphilis, and in 5% of those with benign tertiary syphilis.

The condition is characterized by impairment of proprioception, and vibration sense; Argyll Robertson pupils, which react poorly to light but well to accommodation; and decreased muscle tone (hypotonia) and diminished reflexes (hyporeflexia). There may be a wide-based gait and inability to walk in the dark. The condition is also characterized by paresthesias, analgesia, or sharp recurrent muscle pains in the legs which may be described as shooting. There may be crisis in several body systems. The crisis may begin suddenly, lasting for hours or days, and cease abruptly. The gastric crisis is characterized by sharp abdominal pains and nausea and vomiting. The laryngeal crisis is characterized by a sudden, periodic cough and dyspnea. The urethral crisis is characterized by painful bladder spasms. There may be a neurogenic bladder with overflow and the inability to control urination. Impairment or dysfunction of the bowels and genitals may occur. Painless, trophic ulcers over pressure points on the feet develop and there may be joint damage.

Diagnostic tests for syphilis include: a clinical history and physical examination; serologic tests; investigations of sexual contacts; and, if appropriate, dark-field examination of fluids from lesions. Cerebrospinal fluid (CSF) tests and x-ray examinations may also be done. Serologic tests for syphilis (STS) aid in diagnosing syphilis and other related treponemal diseases.

The treatment is the same as for neurosyphilis, and may include antibiotics, antipsychotics and analgesics. Patients under treatment are observed for Jarisch-Herxheimer reaction to the treatment.

There may be repeated tests performed on CSF. There may also be progression of sclerosis of the posterior columns of the spinal cord. Neurosyphilis, involving essential parts of the neurological system, generally affects patients in their 40s or 50s. The condition is manifested by progressive deterioration in behavior, and may mirror a psychiatric illness or Alzheimer's disease. Convulsions, difficulty communicating (verbally or otherwise), or transient weakness on one side of the body may occur. Irritability, difficulty in concentrating, deterioration of memory, defective judgment, headache, insomnia, or fatigue and lethargy more commonly appear. The patient's hygiene and grooming deteriorate. Emotional instability, resulting in lack of strength, depression, and delusions of grandeur with lack of insight, may occur.

• In those cases where there is severe neurologic deficit, consider entitlement under 38 CFR 3.350 [Special monthly compensation ratings]; competency under 38 CFR 3.353 [Determinations of incompetency and competency]; and ancillary benefits under 38 CFR 3.807, 38 CFR 3.808 [Automobiles or other conveyances; certification], 38 CFR 3.809 [Specially adapted housing], and 38 CFR 3.809a [Special home adaptation grants].

• Rate upon the severity of convulsions, paralysis, visual impairment or psychotic involvement, etc.

• It is required for the minimum ratings for residuals under diagnostic codes 8000-8025, that there be ascertainable residuals. Determinations as to the presence of residuals not capable of objective verification, i.e., headaches, dizziness, fatigability, must be approached on the basis of the diagnosis recorded; subjective residuals will be accepted when consistent with the disease and not more likely attributable to other disease or no disease. It is of exceptional importance that when ratings in excess of the prescribed minimum ratings are assigned, the diagnostic codes utilized as bases of evaluation be cited, in addition to the codes identifying the diagnoses.

• Disability in this field is ordinarily to be rated in proportion to the impairment of motor, sensory or mental function. Consider especially psychotic manifestations, complete or partial loss of use of one or more extremities, speech disturbances, impairment of vision, disturbances of gait, tremors, visceral manifestations, injury to the skull, etc. In rating disability from the conditions in the preceding sentence refer to the appropriate schedule. In rating peripheral nerve injuries and their residuals, attention should be given to the site and character of the injury, the relative impairment in motor function, trophic changes, or sensory disturbances.  38 CFR 4.120

• With the exceptions noted, disability from the following diseases and their residuals may be rated from 10 percent to 100 percent in proportion to the impairment of motor, sensory, or mental function. Consider especially psychotic manifestations, complete or partial loss of use of one or more extremities, speech disturbances, impairment of vision, disturbances of gait, tremors, visceral manifestations, etc., referring to the appropriate bodily system of the schedule. With partial loss of use of one or more extremities from neurological lesions, rate by comparison with the mild, moderate, severe, or complete paralysis of peripheral nerves” 38 CFR 4.124a