Journal of Neurology. NeurosurgerY,1 tUl PsYchiatriy 1988;51:1097-1099

Short report

Tabes dorsalis: electrodiagnostic featuresPETER D DONOFRIO, FRANCIS 0 WALKER

From the Department ofNeurology, Wake Forest University, Bowman Gray School of Medicine, WinstonSalem, North Carolina, USA

SUMMARY Electrodiagnostic data have not been previously reported in tabes dorsalis. A patientwith tabes dorsalis is described whose nerve conduction studies and median nerve somatosensoryevoked responses (SEPs) were normal. H-reflexes were absent. SEPs of the tibial nerve suggestedposterior column dysfunction. These electrodiagnostic findings correlate precisely with the knownpathology of tabes dorsalis.

Although tabes dorsalis is the most common neu-rological expression of tertiary syphilis,' no reportsexist of its clinical electrophysiology. Since the symp-toms and signs of tabes dorsalis mimic those of severeperipheral neuropathy or myelopathy, patients withtabes dorsalis may be referred for electrodiagn6sis.We describe the electrodiagnostic findings in this dis-order.

Case presentation

A 54 year old woman was referred for poor balance, legweakness and pain, recurrent left knee effusions, and a pre-vious history of "polio". She developed weakness of bothlegs at age 7 years, diagnosed as "polio". Several years later,she began to experience diminished lower extremity sensa-tion and gait deterioration.

Several years after onset of the disease, bladder distensionand overflow incontinence further complicated her illness.Additional disabilities included lower extremity lightningpains, recurrent knee effusions, and chronic toe infectionsnecessitating amputation.

Examination revealed an enlarged left knee, pes cavus andhammer toe deformities, and amputation of both small toes.Pupils were large and unreactive to light and accommo-dation. Dilute pilocarpine did not constrict them. Reflexeswere normal in upper extremities and absent in the legs.Light touch, pinprick, and cold sensation were markedlyreduced in the legs from 5 cm above the patella distally.Vibration sensation was absent distal to the pelvis. Proprio-ception was absent at the great toe and ankle, and markedlyAddress for reprint requests: Peter D Donofrio, MD., Department ofNeurology, Bowman Gray School of Medicine, 300 S. HawthorneRoad, Winston-Salem, NC 27103, USA.

Received 5 January 1988 and in revised form 11 March 1988.Accepted 15 March 1988

reduced at the knee. Coordination was severely impaired inher legs. Her gait was wide-based and unsteady; she wasunable to tandem walk. Romberg manoeuvre demonstratedprofound instability.

Routine blood and urine studies were normal. Serumfolate level was normal as was Schilling's Test, Part 1. SerumVDRL was non-reactive (VDRL was reactive in a previoushospitalisation). Serum microhaemagglutination-Treponema pallidum (MHA-TP) was positive. Cerebrospinalfluid (CSF) analysis revealed no cells, a protein of 0-24 g/l(normal <0 45), and a non-reactive VDRL. Thoracic andlumbosacral spine myelography, CT, and MRI were normal.

Sural, median, and ulnar sensory and peroneal and poste-rior tibial motor nerve conduction studies were normal.Actual values (amplitude, distal latency, conductionvelocity, respectively; normal values in parentheses) were:sural 15 pV (.6), 3-4 ms (<4 2); median sensory 45 pV(.22), 2 5 ms (<3-4), 62 m/s (.53); ulnar sensory 30 pV(.10), 2-5 ms (<3 2); peroneal motor 5 mV (.2), 4 5 ms(<6-1), 51 m/s (.41); and posterior tibial 4mV (.3), 39 ms(<62), 47 m/s (.41). F-response latencies were normal:peroneal 45 6 ms (< 56) and posterior tibial 47-6 ms (< 58),but posterior tibial nerve H-reflexes were absent.Median nerve somatosensory evoked potentials (SEPs)

were normal, yet posterior tibial nerve SEPs demonstratedposterior column dysfunction (fig). EMG was unremarkableexcept for minimal spontaneous activity in both medial gas-trocnemius muscles. Needle examination of lumbosacralparaspinal muscles was normal.The patient's pupillary, neurological, urological, ortho-

paedic, and serological manifestations confirmed the diag-nosis of tabes dorsalis. She denied previous syphilis injection,but subsequent questioning of relatives uncovered apreviously-undisclosed history of syphilis in both maternalgrandparents and her mother, in the latter case during thepatient's childbirth. Because of the uncertainty of previoustreatment, the patient received a full course of intravenousand intramuscular penicillin.

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l may be asymptomatic and may not manifest signsn nerve commonly associated with congenital syphilis. Even

though most features of tabes dorsalis do not developuntil 10-25 years after primary infection, this latencymay be as short as 5 years in children.3

Serological findings are variable in tabes dorsalisdepending on the clinical activity and duration of thedisease.' Since MHA-TP detects antibodies specificfor Treponema pallidum, reactivity persists regardlessof disease duration, severity, or previous treatment.

512 Conversely, VDRL is non-reactive in 25 to 57% ofpatients with late syphilis. ' 4-6 CSF analysis may besimilarly insensitive in tabes dorsalis. A nonreactiveVDRL and acellular count is not unusual particularly

2-uV in "burnt out cases".1 In Merritt's series of 100+ patients with tabes dorsalis, CSF serology was non-

-I--rI reactive in 28 patients and a normal WBC count was40 50 observed in 53 patients.3

In addition to the classic symptom and sign triads,our patient displayed other features of tabes dorsalis.

l These included severe nociception loss in the legsierve resulting in painless trauma, recurrent toe infections,

and amputation of several toes. Recurrent left kneeeffusions probably represented an early Charcot joint,although radiographs did not confirm destructivechanges. Distal weakness and atrophy may be latemanifestations of tabes dorsalis, attributed to exten-sion of the syphilitic process to anterior horn cells ormotor roots.3

Clinical electrophysiology has not been previouslyreported in tabes dorsalis. Dyck recorded normalamplitude and conduction velocities of A alpha, Adelta, and C fibres in vitro from the sural nerve of a

tabetic patient._ A neurophysiological-pathological correlation

2uV I emerges from the electrodiagnostic results in this case-i-----". . and the known pathology of tabes dorsalis. Abnor-40 50 mality in tabes dorsalis is concentrated in the dorsal

roots, dorsal funiculi, and posterior columns of thefined lumbosacral and lower thoracic spinal cord.3 8 Usu-Erbds point ally spared are the anterior horn cells and ventralnulation. roots.8 The dorsal root ganglia are rarely affected toe responses a significant degree and individual ganglion cells dor the scalp. not show features of degeneration.9 1o Stern identified

inflammation in the dorsal root ganglia from only oneof nine patients with tabes dorsalis.9Normal sensory conduction studies verify integrity

f symptoms of the sensory nerves and dorsal root ganglia. Absentlerritt, that H-reflexes can be attributed to atrophy of the dorsalid dysuria) roots in the sacral area, preventing entry of the sen-pprioceptive sory arc of the H-reflex. Absent cortical SEPs on tibialiysiological nerve stimulation are explained by posterior columnvious polio degeneration. Normal median nerve SEPs confirmed syphilis integrity of the sensory pathway in the cervical areamptoms of through the dorsal columns to the somatosensory-ted at birth cortex. Motor conduction studies are normal since

C3-Fz

CII-Fz

CvI- Fz

Erb-Fz

Fz- Cz

T12 - ipsi. hip

L3- ipsi.hip

Pbplitealfossa I,,l , io ,

v 10 20 30Time (ms)

Fig Somatosensory evoked potentials: Well-dejresponses (two trials each) were recordedfromthe spine, and the scalp on left median nerve stiiLeft tibial nerve stimulation produced recordablkat the poplitealfossa, L3 and Tl2, but none over

Discussion

This patient manifested the classic triads ofand signs of tabes dorsalis described by Mis, symptoms (lightning pains, ataxia, ar

and signs (tabetic pupils, areflexia, and proloss).2 Since her clinical and electrophpresentation was incompatible with preNmyelitis, we hypothesise that she acquircongenitally and experienced her first syitertiary disease at age 7 years. Infants infec

Left tibial n

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I . .-. . .

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Tahes dorsalis: electrodiagnostic flatures

motor fibres are rarely affected in tabes dorsalis.Fibrillation potentials in the gastrocnemius musclescould be explained by superimposed S, radi-culopathies, but absence of S1 root abnormality inproximal and paraspinal muscles argues against thisexplanation. A more plausible interpretation wouldbe partial anterior horn cell involvement known tooccur in some cases of tabes dorsalis.3

Pupillary abnormalities excluded, tabes dorsalismimics peripheral neuropathy, spinal cord disease,and lumbo-sacral polyradiculopathy. Tabes dorsalisshould be considered in any patient manifesting theelectrodiagnostic triad of normal nerve conductionstudies, absent H-reflexes, and impaired posteriorcolumn conduction.

References

1 Simon RD. Neurosyphilis. Arch Neurol 1985;42:606-13.2 Merritt HH. A Textbook of Neurology. 2nd ed. Philadel-

phia, Lea & Felsiger, 1950:129-53.3 Merritt HH, Adams RD, Solomon HC. Neurosyphilis.

New York, Oxford University Press, 1946.4 Hooshmand H, Escobar MR, Kopf SW. Neurosyphilis:

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a study of 241 patients. JAMA 1972;219:726-9.5 Luger A, Schmidt B, Spendlingwimmer I, Horn F.

Recent observations on the serology of syphilis. Br JVen Dis 1980;56:12-16.

6 Sparling PF. Diagnosis and treatment of syphilis. N EnglJ Med 1971;284:642-53.

7 Dyck PJ, Lambert EH, Nichols PC. Quantitative mea-surement of sensation related to compound actionpotential and number and sizes of myelinated andunmyelinated fibres of sural nerve in health,Friedreich's ataxia, hereditary sensory neuropathy,and tabes dorsalis. In: Cobb WA(ed). Handbook ofElectroencephalography and Clinical Neurophysiology.Vol. 9, Somatic Sensation, Amsterdam, Elsevier Pub.Co., 1971:83-117.

8 Greenfield JG. Infectious diseases of the centralnervous system. In: Blackwood W, McMenemey WH,Meyer A, Norman RM, Russell DS. Greenfield'sNeuropathology. 2nd ed, Baltimore, Williams andWilkins Co, 1963:164-81.

9 Stern RO. A study of the histopathology of tabes dor-salis with special reference to Richter's theory of itspathogenesis. Brain 1929;52:295-316.

10 Hassin GB. Tabes dorsalis, pathology and pathogenesis,a preliminary report. Arch Neurol PsychiatrY 1929;21:311-41.

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