Infections of the Central Nervous System (Neurosyphilis)

Infections generally involve the invasion of pathogenic microbes into the body systems or organs, causing damage or alteration in the body or system functions. The Nervous system is not an exception and one of the invasive disorders is the syphilitic lesions which causes Neurosyphilis and out of the many infections which occur due to this, is the Meningovascular syphilis (Early tertiary neurosyphilis).

Neurosyphilis

Involvement of the nervous system in syphilis used to be common before the 1950's, but now it is distinctly uncommon to see fresh cases. Neurological lesions are caused by invasion of the tissues by T.pallidum. Neurological involvement occurs in 4% of cases of syphilis left untreated. Men are affected 4-5 times more than women. Meningovascular involvement is more common in India, constituting 60-70% of the total.

Syphilitic lesions

1. Secondary stage-meningitis
2. Tertiary stage
I. Meningovascular syphilis: Cerebral forms-Basal meningitis, pachymeningitis, vascular thrombosis due to endarteritis, optic atrophy and gumma. Spinal forms-Meningomyelitis, Erb's paraplegia, cervical pachymeningitis, syphilitic amyotrophy, radiculitis and gumma.
II. Parenchymal involvement: Cerebral form-General paralysis of the insane (GPI). Spinal form-Tabes dorsalis, Optic atrophy.
3. Congenital syphilis- Meningovascular involvement, optical atrophy, deafness, general paralysis of the insane and tabes dorsalis.

Meningovascular syphilis (Early tertiary neurosyphilis)

In this form, the more common lesion is leptomeningitis. Lesions occur over the base of the brain and over the hemispheres. The basal meningitis may involve the cranisl nerves leading to cranial nerve palsies and occlusion of the foramina leading to internal hydrocephalus. Main lesion is endarteritis obliterans. The intima is thickened, the vessel wall shows infiltration by lymphocytes and plasma cells. Thrombosis supervenes and this occludes the lumen. granulomatous changes are also seen. Less commonly, the duramater over the cerebral hemispheres may be involved in the granulomatous process leading to thickening (cerebral pachymeningitis).

Clinical features

Cerebral forms : Syphilitic meningitis is seen in the age group of 18-40 years. Syphilitic basal meningitis leads to a subacute or chronic meningitis characterized by headaches, cranial nerve palsies, elevated intra-cranial tension and signs of meningeal irritation. The CSF shows raised proteins and lymphocytic pleocytosis. The sugar and chloride are normal. Cranial pachymeningitis causes headache, seizures and focal neurological deficits such as dysphasia or hemiparesis. Syphilitic endarteritis is one of the causes of occlusive cerebrovascular lesion in the young. These cases present features of cerebral thrombosis. Lower motor neuron facial palsy and trigeminal neuralgia may occur. The prognosis for recovery is good if the condition is diagnosed in time and treated.

Spinal forms : This gives rise to the picture of acute transverse myelitis or varying degrees of cord compression with root pains. In some, spastic paraplegia developments. In this form (Erb's syphilic paraplegia) bladder dysfunction is common, but sensory symptoms are rare.

Hypertrophic cervical pachymeningitis : Compression of the cervical cord leads to root pain, weakness and wasting of the upper limbs and shoulder girdle and paraparesis. Such a picture is also referred to as syphilitic amyotrophy. The cauda equina may be involved leading to root pain, areflexia, weakness and wasting affecting the thighs and legs.

Optic atrophy : This may result from meningo-vascular or parenchymal involvement. The former leads to arachnoiditis, optic neuritis or retrobulbar neuritis. These changes occur early during the tertiary stage of syphilis. At this stage, specific treatment may help in reversing the condition. Optic atrophy occurs as a part of the parenchymal involvement during the late stages.