Diagnosis of Toxoplasmosis (Serologic Examination, CT, MRT and NLS)

T.I. Pankova,

A.S. Sosnovskaya

Toxoplasmosis is a parasitic disease whose causative agent is toxoplasma (Toxoplasma

condii Nicolle et Manceaux), which belongs to protosa. The disease typically has a chronic

course, nervous system lesion, lymph-adenopathy and enlarged liver and spleen. Quite often

myocardium, muscles and eyes are affected.

The infection is mostly transmitted through the alimentary tract. Yet there are some

instances recorded where contagion occurred through the injured skin and mucous

membranes. Toxoplasma is apt to form cysts in tissues causing a latent infection

condition. The parasite becomes active in the conditions adverse to the macro-organism

and with its immune responsiveness going down. In the pathogenesis of the toxo-

plasmodial lesion of the central nervous system of importance are local inflammatory

occurrences, dis-circulatory disturbances related to vasculitis and blocked liquor tracts

leading to hydro- or micro-cephaly.

Clinically, the lesion of the central nervous system manifests itself as meningitis,

encephalitis, meningeonciphalitis and encelphalomyelitis.

The most typical form of toxoplasmosis of the central nervous system is

meningeonciphalitis, which clinical picture contains general cerebral and meningeal

symptoms, paresis and limb paralyses, tonic and clonic spasms, opticokinetic-(diplopia) and

coordination disturbances. The blood test reveals a left-shifted leukocytosis and increased

ESR: the cerebrospinal fluid contains lymphocytic pleocytosis and a

moderately increased protein content.

In diagnosing toxoplasmosis of importance are cranial radiography, serological

investigation, pneumoencephalography, CT and MRT. However, it is the NLS-

investigation of cerebral structures that plays the most important part in the diagnosis. Of

great diagnostic importance is a substantially increased spectral similarity to the

reference standard ‘tomoplasma gondii’ (D< 0.425).

The toxoplasmosis should be discriminated from viral encephalitis, encephalomyelitis and

meningitis.

In the MRT-investigation toxoplasmosis is manifested by a progressive multi-focal

encephalopathy. With toxoplasmosis the typical cases have to do with granulomatous

fields which are small: 2.0 cm or less in diameter. On NLS image these formations look

like hyperchromatic areas (6 points on Flandler’s scale) with the central necrosis zone in

ring-shaped structures being visible as an area of lower chromogenic density (4-5 points).

Hemorrhage areas of small size are quite typical. The above-mentioned changes are

48localized peri-and para-ventriculary, often in the region of bordering cortico-medullary

structures as well as in the regions of basal ganglia.

Clinical observation

Patient K., born in 1974. The preliminary diagnosis when admitted into the neurological

department as acute cerebral circulation disturbance in the spinal artery basin.

The patient complained of weakness in left limbs, speech impediment, asthena and loose

cough. According to her wording she fell ill (Feb. 06.01) when she stopped talking,

developed weakness in left limbs, diplopia and disturbed swallowing. The anamnesis

read a developed right-side hemiparesis, that passed off by itself within two weeks.

The patient is in grave condition. Neurological status: conscious, understands when she

hears people speaking to her, but dosen’t speak. Cranial nerves: equal palpebral fissures,

nystagmus not present, the right nasolabial fold smoothed out. Slight deviation of the

tongue to the right. High tendon and periosteal extremity reflexes, weakness in right

limbs. Reduced pharyngeal reflex on both sides. Rigidity of occipital muscle is

moderately frank. Kering’s symptom on both sides. Babinski’s reflex on the left.

Laboratory investigation:

Clinical blood analysiss: erythrocytes - 3.96x10.12/1, hemoglobin - 127 g/l: -0.9: L -

5.6x10.9/1, ESR - 32 mm/g. - 1; - 74; - 21; - 2; -2.

Biochemical blood test: glucose - 4.6 mm/1; urine - 6.6 mm l/1, bilirubin - 13.38; - 5.5; -

7.85 mmo1/1; creatinine - 0.066 mmo1/1, total protein 70.0mg/1; albumin - 5.5;

globulins - 44.8; L2 - 4.8; L2 - 7.7, B - 11.8; J - 20.5; - 1.24; - 0.29 mmo1/1; - 0.31

mmo1/1.

Test for toxoplasmosis detected antibodies with rising antibody titer in dynamics (1:21 -

1:400).

Cerebrospinal - 2.5 mmo1/1; chlorides 0 1.24 mmo1/1, protein - 0.2 g/l, sugar 0 4.1

mmo1/1. Cellular composition: cytosis 0 213, L - 1.2; erythrocytes - 4.5.

MRT-investigation of the encephalon (of 16 Feb.01) in T-2 picture on both sides,

detected paraventriculary and subcortially multiple unequal-sized roundish nodi (from 0.5 to

2.0 cm) producing an unevenly increased MR-signal. Similar nodi were detected in

the dorsal part of the pons on the left and in the basal regions of the frontal lobes. In the

formal lobe the examination subcortially detected an ellipsoidal cyst 1.2x0.5 cm. In the

T-1 picture of the field the nodi detected in the T-2 picture produced a slightly diminished

MR-signal and was clearly outlined. Upon administration of magnevist some nodi, not

visualized in the T-1 picture, manifested themselves by uniform amplification of the MR-

signal, the others produced an amplification in the form of a thin ring or a small

amplification in the center.

49The cyst did not respond to administration of the contrasting agent. The central regions of

the granulumatous fields represented by necrotic zones were more hyperintensive in

the T-2 picture and after the contrasting agent administration did not accumulate it,

signal amplification occurred in the peripheral regions in the form of a thin ring. The

lateral ventricle bodies were not quite clearly enlarged. The median structures did not

appear to be shifted.

In the frontal lobe on the right NLS picture shows subcortically detected hyperchromatic areas

(6 points) surrounded by a perifocal edema zone (3-4 points) detected in the dorsal part of

the encephalon on the right. A spectral similarity to the standard reference

process “toxoplasma gongii” (D <0.183) was found, which allowed to confirm the

diagnosis of toxoplasmosis.