SYPHILIS

This infectious disease is caused by the spirochaete Treponema pallidum. Entry is by :

- Inoculation through skin or mucous membrane (sexually transmitted) - acquired syphilis

- Transmission in utero - congenital syphilis

Spirochaetal Infections of the Nervous System

In the last 30 years, there has been a steady decline in incidence regardless of race and ethniciry

Despite this, it still remains an important health problem in certain geographic areas

Up to 10% of patients with HIV will test positive for syphilis. All patients with neurosyphilis should be tested for this

The chancre or primary sore on skin or mucous membrane represents the local tissue response to inoculation and is the first clinical event in acquired syphilis

The organism, although present in all lesions, is more easily demonstrated in the primary and secondary phases

In congenital syphilis fetal involvement can occur even though many years may elapse between the mother's primary infection and conception

Widespread recognition and efficient treatment of the primary infection have greatly reduced the late or tertiary consequences

Not all patients untreated in the secondary phase progress to the tertiary phase

In HIV patients the neurological complications occur earlier and advance more quickly

Investigations :

Spirochaetes can be demonstrated microscopically by dark field examination in primary and secondary phase lesions

Serological diagnosis depends on detection of antibodies

1. Non-specific (Reagin) antibodies (lgG and IgM)

Reagin tests involve complement fixation.

The Venereal Disease Research Laboratory (VDRL) test is the commonest and when strongly positive indicates active disease

(may be negative in HIV)

2. Specific treponemal antibodies (do not differentiate between past and present infection). Fluorescent treponemal antibody absorption (FTA) test and Treponema immobilisation (TPI) test.

3. Treponema pallidum DNA can be detected in the CSF of patients by PCR (sensitiviry 60%)

Spirochaetal Infections - Neurosyphilis

The initial event in neurosyphilis is meningitis. Of all untreated patients 25% develop an acute symptomatic syphilitic meningitis within 2 years of the primary infection.

Meningovascular Syphilis :

'Early' late manifestation resulting in an obliterative endarteritis and periarteritis

Presents as a 'stroke' in a young person - hemisphere, brain stem or spinal. Granulations around the base of the brain may produce cranial nerve palsies or even hydrocephalus

CSF - lymphocytes 100/mm3, protein , gammaglobulin , positive serology. Penicillin arrests progression

Spinal Syphilis :

Chronic meningitis with subpial damage to the spinal cord.

Presents as a progressive paraplegia, occasionally with radicular pain and wasting in upper limbs - ERE's PARAPLEGIA. CSF - as meningovascular syphilis. Penicillin arrests progression

Ocular Manifestations :

Meningitis around optic nerve with subpial necrosis may be the only manifestation of late syphilis. Presents as a constriction of the visual fields with a progressive pallor of the optic disc:

- if both eyes are affected, the vision is rarely saved

- if only one eye is involved, treatment with penicillin will save the other

Neuroretinitis, uveitis and chorioretinitis occur, especially in HIV patients

General Paresis :

Characterised by dementia - with memory impairment, disordered judgement and disrurbed affect - manic behaviour, delusions of grandeur (rare).

There are two phases :

1. Pre-paralytic - with progressive dementia.

2. Paralytic - when corticospinal and extrapyramidal symptoms and signs develop

associated with involuntary movements (myoclonus)

Argyll Robertson pupils may be present

At autopsy, meningeal thickening, brain atrophy and perivascular infiltration with plasma cells and lymphocytes are evident; culture from the cortex may reveal an occasional treponema

CSF -lymphocytes 50/mm3, protein 0.5-2 g/I, gammaglobulin

Reagin tests in CSF positive in the majority

Treatment in the preparalytic phase will halt progression in 40%

Spirochaetal Infections

Lime Disease (Neuroborreliosis) :

Originally described in the community of Old Lyme, this is a disorder, caused by the spirochaete Borrelia burgdorferi, characterised by relapsing and remitting arthralgia associated with a characteristic skin rash (erythema chronicum migrans) and neurological features. The organism, related to the treponemes, is prevalent throughout Europe and North America and is carried by ixodes ticks

Diagnosis :

A combination of abnormal liver and renal function with elevated creatine kinase suggest the diagnosis. Leptospirae can be isolated from blood and CSF (in the immune phase) but diagnosis is usually confirmed by demonstrating agglutinating antibodies (ELISA detected IgM)

Treatment :

The disease is usually self limiting and therapy unnecessary. Early treatment in the leptospiraemic phase with Penicillin G 12 million units daily and tetracycline 500 mg four times per day may minimize the immune-mediated complications. Support of hepaticlrenal failure and management of haemorrhagic complications may be life-saving