Brain stem tuberculoma presenting with isolated ocular motility abnormality: A series of two cases and review of literature.

Introduction

Tuberculosis is still endemic in developing countries such as India and tuberculomas account for up to 40% of space occupying intracranial masses.[1] Isolated brain stem tuberculomas are rare lesions and account for about 5% of all intracranial tuberculomas.[2] These intracranial lesions commonly present as oculomotor and other cranial nerve palsies,[34] unilateral saccadic paralysis, one and a half syndrome, other ocular signs, and neurological deficits. In this article, the authors describe two cases of isolated ocular motility abnormality due to brain stem tuberculoma.

Case Reports

Case 1

A 25-year-old female presented with a complaint of double vision on right lateral gaze for 2 months. She was non-hypertensive and non-diabetic. On examination, she had visual acuity of 6/6 in both eyes. Right pupil was 1.0 mm larger slightly in size than left and showed sluggish reaction to light and near stimulation. There was right hypertropia of 10 PD which increased on right gaze and left head tilt suggesting right inferior rectus palsy. There was restriction on depression of right eye in abduction. There was no limitation of movement in the left eye. There was no ptosis. Rest of the ocular examination was normal. Magnetic resonance imaging (MRI) brain revealed a ring enhancing lesion in the ventral midbrain, in the area of tegmentum at the level of superior colliculus, with perilesional edema [Figure 1]. X-ray chest and ultrasound of the abdomen was normal. The patient did not have any feature of immunocompromised state. On the basis of MRI findings and the endemicity of tuberculosis in our country, a presumptive diagnosis of tuberculoma of the midbrain was made. Antitubercular treatment consisting of rifampicin, isoniazid, ethambutol, and pyrizinamide was started and on review 3 months later, her double vision and pupillary abnormalities had resolved completely. The treatment was continued for total of one and half years. Follow-up MRI performed at the end of 1 year showed complete resolution of the lesion. MRI was repeated before the stoppage of treatment that is after 2 years and that also revealed complete resolution of the lesion.

Figure 1

Magnetic resonance imaging brain T1 contrast sequence showing a ring enhancing lesion of 5.0 mm size in the ventral midbrain in the area of tegmentum at the level of superior colliculus with perilesional edema

Case 2

A 48-year-old male presented with complaints of inability to turn his eyes toward the left side. He did not complain of diplopia. His visual acuity was normal 6/6 in both eyes. Pupils were 3.0 mm in size and reaction fundii were normal in both eyes. Ocular movements revealed left gaze palsy with rotatory nystagmus to left. His face was turned to the left side. The oculocephalic maneuvers and horizontal caloric stimulation produced no eye movement. Rest of the examination was normal. MRI brain revealed intensely enhancing nodular lesions measuring 1 cm in diameter in the pons [Figure 2]. Image-guided biopsy of the lesion showed caseating granuloma which on special staining showed acid fast bacilli. Patient was given antitubercular treatment consisting of rifampicin, isoniazid, ethambutol, and pyrizinamide anti-tubercular treatment. Follow-up MRI at 6 months showed disappearance of the lesion. However, there was no improvement in the left gaze palsy.

Figure 2

Magnetic resonance imaging brain showing intensely enhancing nodular lesion one at the lower pons

Discussion

Tuberculomas are usually located in the cerebral or cerebellar hemisphere due to the high blood supply to these areas. The brain stem is an uncommon location for tuberculomas.[2] Only three cases have been reported in the literature where brainstem tuberculoma presented with isolated ocular movement abnormality.[5-7] Table 1 summarizes the details of these cases.

Table 1

Summary of the three cases presenting with ocular motility abnormality with brain stem lesions

The clinical picture in our case favors the proposed transverse neuroanatomic organization of the fasicular fibers of the oculomotor nerve proposed by Castro et al.[1] That is, mediolateral samatotopy with superior rectus and inferior rectus being the most lateral and caudal, and the pupilloconstrictor fibers and the inferior rectus being the most medial and rostral. The tuberculoma in our patient was located in ventral midbrain tegmentum on right side near the midline where fibers of pupilloconstrictor and inferior rectus are situated.

Our patients presented with a rare clinical presentation of brainstem tuberculoma in the form of an isolated ocular motility abnormality with pupilloconstrictor paresis. This isolated single extraocular muscle paresis is seen commonly in infarction or hemorrhage of brain stem.[34] Our patients have symptoms and signs correlating with the site of the tuberculoma. The clinical presentation of our patient supports the accepted topographical fascicular arrangement of the oculomotor nerve in the midbrain tegmentum.

The important differential diagnosis of intracranial ring enhancing inflammatory lesion is neurocysticercosis which are thin-walled, fluid-containing cysts and sometimes have scolex inside. In contrast to these, tubercular lesions are thick-walled, conglumoerate lesions.

The treatment of tuberculoma is usually medical. A course of antitubercular therapy for one and half years is sufficient.[8] Most of the times, the lesions resolve with medical treatment only. Surgical intervention is required only in the cases where the diagnosis is in doubt. However, in most of the cases, the clinical scenario and radiological findings are sufficient to start medical treatment. Most of the patients respond well with medical therapy like in our case 1, and surgical intervention is not required.[2] Role of steroids in tuberculoma is controversial; however, it is indicated in cases of associated extensive perilesional edema.