CNS Infections – General Paralysis of the Insane (GPI), Dementia Paralytica and Tabes Dorsalis

GPI is more common than tabes dorsalis. Men above 40 years are more affected, while in tabes dorsalis, it develops 10-20 years after the primary infection and also Males are affected five times more frequently than females.

General paralysis of the insane (GPI), Dementia paralytica

Here, the frontal and temporal lobes of the brain show diffuse cortical atrophy with gliosis. The meninges show thickening and lymphocytic infiltration. Ventricles show dilatation and ependymitis. In about 50% of cases, the organisms (T.pallidum) can be demonstrated in brain biopsy specimens.

Clinical features: The higher mental faculties deteriorate gradually, leading to reduction in intellectual capacity, loss of memory and personality changes. These patients show lack of judgement and insight. Euphoria, lack of judgement, loss of inhibition revealed by abnormal social behavior, dementia, depression or mania may develop. Less commonly grandiose delusions may be the prominent features. The pupillary changes are characteristic. Around 50% of cases show Argyll Robertson pupil. The pupils are small, irregular, unresponsive to light reflex, but responsive to accommodation. Optic atrophy occurs in 5-10% of cases, seizures develop in 50%. The limbs, lips and tongue may be tremulous. The to and fro movements of the tongue are described as “trombone tremor” since this bears similarly to the musical instrument-trombone.

Congestive episodes occur from time to time. These manifest as focal neurological deficits such as hemiparesis, dysphasia or hemianopia. These recover spontaneously. Syphilic aortic lesions may coexist in 30-50% of cases. The course of the disease is one of gradual progression with fluctuations proceeding to incapacitation.

Tabes dorsalis

This form of parenchymal neurosyphilis is less common than GPI and it develops 10-20 years after the primary infection. Males are affected five times more frequently than females.

Pathology: The posterior root ganglia of the spinal cord show inflammation. Later, the posterior roots and the posterior columns of the spinal cord undergo atrophy.

Clinical features: Initial symptoms are pain and paraesthesia in the limbs. As the condition proceeds, sensory ataxia sets in. The patient reveals loss of posterior column sensations. The gait is stamping in quality. The ankle jerks and knee jerks are lost, the former is abolished earlier. The Limbs are hypotonic. Romberg’s sign is positive. Argyll Robertson pupil may be present in many. Optic atrophy occurs in a few cases. There is loss of deep tenderness and squeezing the tendo-Achilles does not cuase the characteristic pain (Abadie’s sign). Testicular sensation is lost. Some patients reveal loss of touch and delay in the appreciation of pinprick over the central parts of the face, Ulnar border of the hands, distal parts of the legs, perianal region and over the chest. Autonomic disturbances may develop.

Bladder sensation is lost early and therefore atonic distension and urinary incontinence may develop. Impotence occurs early. Partial ptosis develops due to paralysis of sympathetic nerves supplying the Muller’s muscles of the eyelid. Many patients overcome the disability caused by partial ptosis by tilting the head backwards and wrinkling the forehead. This is described as the “tabetic facies”. Due to loss of trophic influences, the major joints develop painless swelling and undergo degenerative changes-Charcot’s joints. Painless trophic ulcers develop in the feet and other areas of pressure.

The smooth course of the disease is often disturbed by the occurrence of lightening pains, which are unique for tabes dorsalis. These are lacerating pains occurring in transverse directions in the limbs, chest, and face. Lightening pains differ from neuralgic pains in that the former do not follow the direction of nerve roots or trunks. Visceral crises develop frequently. Gastric crisis is characterised by severe epigastric pain and vomiting. Rectal crises gives rise to tenesmus. Stridor develops as a result of laryngeal crisis.