Tabes dorsalis

In the prepenicillin era, tabes dorsalis accounted for about one-third of patients with neurosyphilis. Among several hundred patients with neurosyphilis treated in neurologic clinics in Poland from 1956 to 1965, tabes was the most frequent diagnosis (44%), although in the majority; the process appeared to have “burned out,” that is, the disease no longer progressed and CSF abnormalities were absent, either spontaneously or as a result of the incidental use of antibiotics. In a study of late complications of syphilis involving about one-third of the population of Finland between 1963 and 1968, 66 cases of neurosyphilis were identified; of these, two thirds involved tabes dorsalis. In the 1960s, 30 cases of neurosyphilis (10 of tabes) were seen in one regional neurological center in England over a 3.5 year period. Over the next 8.5 years, only 16 cases, including four of tabes, were encountered. This condition is now a rarity in most of the developed world.

 

Symptoms and signs 

 

The onset of symptoms of tabes occurs in the majority of untreated patients after a latent period of 20-25 years. The early clinical features are lightning pains, paresthesias, diminished deep tendon reflexes, and poor pupillary responses to light. In more advanced stages, other symptoms and signs becomes prominent. Lightning pains are sudden paroxysms of severe stabbing pains lasting for a few minutes at a time. These pains usually occur in the lower extremities but may be felt anywhere. They may occur at long intervals or may persist in attacks lasting for several days at a time. Treatment with carbamazepine or related drugs may be effective. Paresthesias are frequently felt on the legs or trunk. Hyperesthesia may be present in the areas involved by lightning pains; such areas may serve as trigger zones that precipitate bouts of pain when touched.

Visceral crises are related to lightning pains, tending to recur in attacks of marked severity that may mimic acute surgical emergencies. The most common form is a gastric crisis consisting of intense epigastric pain, nausea, and vomiting. Intestinal crises (abdominal pain and diarrhea), rectal crises (painful tenesmus), and laryngeal crises (pain in the larynx, hoarseness, and stridor) are rare.

Loss of vibration sense and inability to feel passive movement in joints are among the first detectable signs. Other sensory abnormalities include loss of deep pain perception and development of patchy areas of hypalgesia and hypesthesia over the trunk and extremities. Knee and ankle reflexes are almost always reduced or absent, whereas muscle strength is usually well preserved until the late stages. Plantar responses are flexor; Babinski’s reflex indicates the coexistence of meningovascular syphilis, general paresis, or some unrelated disorder of the CNS.

Ataxia of gait is evident, and results of heel-to-sin and finger-to-nose testing are abnormal. In addition to the broad-based, stamping gait, which becomes worse when patients try to walk in the dark, abnormal findings included diminished vision owing to optic atrophy, Charcot’s joint (unstable, painless, uninflamed, and markedly enlarged joint with overproduction of bone owing to repeated trauma to this anesthetic structure, especially involving the knee), and mal perforans (a painless penetrating trophic ulcer on the plantar surface at the base of a toe). The spine (particularly the lumbar spine) may be the site of Charcot changes, characterized by dense irregular sclerosis large parrot-beak osteophytes, scoliosis, and disk-space narrowing. Although the lesion itself is painless, distressing pain may be produced by impingement of the hypertrophic bone or by a disk protruding on the posterior nerve roots.

Sluggish pupillary reactivity to light is an early finding in tabes; true ARgyll Robertson pupil is a later feature of the disease. Involvement of cranial nerves (particularly the second, third, and sixth) is often overlooked in tabes. Primary optic atrophy appears as sharply defined, grayish white optic disks with conspicuous physiologic cupping, visible lamina cribrosa, and narrowed retinal arteries. If untreated, visual loss progresses to irreversible blindness over months to years. Ptosis and flabbiness of facial muscles probably contribute to a large measure to the so-called tabetic facies. Divergent strabismus may also result from third cranial nerve palsy. Oculomotor weakness is attributed to basilar meningitis, accounting for its occasional improvement after penicillin therapy. Eighth cranial nerve involvement (hearing loss with or without accompanying vestibular abnormalities) is not uncommon.

The time from the onset of tabes to the development of ataxia may be 6 months to 25 years; the longer the duration of the preataxic phase, the slower the subsequent course. In the prepenicillin era, far-advanced tabes was observed with complete incapacitation owing to joint deformity, loss of bladder control, blindness, ataxia, and deafness. Tabes may burn out with time, even in the absence of treatment. Lightning pains may persist even when early treatment has been successful; their presence, therefore , does not indicates continued syphilitic infection. Antibiotic treatment cannot reverse the extensive changes of advanced disease.

 

Laboratory findings

 

The laboratory findings in tabetic neurosyphilis are variable, depending on the stages of tabes, whether partial or full treatment has been administered in the past and whether the process has spontaneously burned out. In the prepenicillin era, negative blood serologic reactions were reported in 12-42% of cases. In a 1972 study of seven patients with long-standing tabes, the blood nontreponemal serology was negative in six patients, all of whom have been treated repeatedly but continued to have lightning pains and other manifestations of tabes.

The CSF findings among 100 patients with tabes, including a large number of patients with old, arrested cases, were 1) lymphocytic pleocytosis in 50% (practically all untreated cases) 2) elevated protein concentration (45-100 mg/dL) in 50%, and 3) reactive nontreponemal serologic test in 72%.

 

Diagnosis and differential diagnosis

 

A clinical diagnosis of tabes is most likely in a patient with lightning pains and ataxia who exhibits findings of absent deep tendon reflexes, Argyll Robertson pupils, and a positive Romberg sign. Early and atypical cases present greater problems in diagnosis, and only the results of serologic testing and spinal fluid examination may lead to the correct diagnosis. A mixed clinical picture of taboparesis may also be a source of diagnostic confusion.

Differential diagnosis includes a variety of neurologic disorders. Although knee and ankle jerks may be lost in meningovascular syphilis of the spinal cord, lightning pains and pupillary changes are not usually present; ultimately, hyperactive reflexes and extensor plantar responses develop. Adie’s syndrome (absent deep tendon reflexes and myotonic pupil) can be distinguished from tabes by the fact that the pupil is not miotic. This syndrome also lacks the lightning pains and ataxia of tabes; serologic tests are negative and CSF examination is normal. Diabetic neuropathy may mimic tabes (diabetic pseudotabes) by producing sluggish reactivity, ptosis, pains and ataxia and by absent deep tendon reflexes. However, in diabetic and other types of peripheral neuropathy, the pain is burning in character rather than shooting, as is typical of tabes, and the serologic findings are negative. Combined system disease is similar to tabes in producing ataxia and bladder disturbances, but lightning pains are not a feature. Extensor plantar responses are found in combined system disease but not in tabes.

 

Symptoms and Signs of Tabes Dorsalis

 

 

Symptoms

Percent

  Lightning pains

75

  Ataxia

42

  Bladder disturbances

33

  Paresthesias

24

  Visceral crises

18

  Visual loss (optic atrophy)

16

  Rectal incontinence

14

Signs
  Pupillary abnormalitites

94

  Argyll Robertson pupils

48

  Absent ankle jerks

94

  Absent knee jerks

81

  Romberg’s sign

55

  Impaired vibratory sense

52

  Impaired position sense

45

  Impaired touch and pain sense

13

  Ocular palsies

10

  Charcot’s joints

7

 

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