A rare case of an internal acoustic meatal tuberculoma involving the VII–VIII nerve complex
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/neuroindia.NI_1273_15
Source of Support: None, Conflict of Interest: None
Tuberculoma of the brain and spine is a common entity, however, very few cases of tuberculoma of the nerves have been reported.,,,, We report the first case of tuberculoma located in the internal acoustic meatus involving the VII and VIII nerve complex. Extensive literature search was performed, which failed to show a tuberculoma at this location.
A 45-year old gentleman presented with unsteadiness of gait, with a tendency to fall towards the left side, for 2 weeks, followed by difficulty in hearing from the left ear for a week, especially while speaking over the phone. On examination, he had left-sided grade 2 (Houseman and Brackman) lower motor neuron (LMN) facial paresis with a left-sided sensorineural deafness as well as the presence of vestibular signs on the left side. An audiogram and speech discrimination score were carried out, which showed a non-serviceable hearing loss in the left ear. Plain and contrast magnetic resonance imaging (MRI) of the brain showed a small ill-defined lesion in the left internal acoustic meatus, which was hypointense on T1 and T2 images; the lesion was enhancing homogenously [Figure 1].
A presumptive diagnosis of vestibular schwannoma was made, and because the lesion was <3 cm in size, he was given the option of gamma knife surgery. The patient opted for surgery and underwent total surgical removal of his lesion by the translabyrinthine approach. Intraoperatively, the lesion was grayish and was involving the VII–VIII nerve complex. Furthermore, the lesion was expanding the nerve and the nerve fibres were firmly adherent to the lesion.
Histopathological examination (HPE) of the lesion showed the expanded nerve fibres with multifocal interstitial and perivascular lymphocytic infiltration, along with ill-formed epithelioid cell granulomas with central necrosis suggestive of a tuberculoma [Figure 1].
He had a persisting grade III LMN facial paresis which was improving, along with a left-sided sensorineural deafness. He was further investigated for the presence of tuberculosis and other granulomatous lesions. The tuberculosis quantiferon test was strongly positive with an elevated erythrocyte sedimentation rate, and the high resolution computed tomography of the chest showed apical lesions with fibrosis suggestive of a previous pulmonary tuberculous infection. Serum acetylcholine esterase assay as well as that of antineutrophilic cytoplasmic and antinuclear antibodies were done to rule out other causes of granulomatous diseases, which were found to be negative. The patient was started on antituberculous treatment.
In a patient with tuberculosis, neuropathy occurs as a complication of meningitis, causing the spinal nerve root and cranial neuropathies (especially cranial nerves II, III, VI, VII, and VIII). Neuropathy is attributed to pressure over the nerves and direct effects of the tuberculous exudates on the nerves. In patients with tuberculosis, neuropathy attributable to direct nerve infiltration has been recognized very rarely in peripheral nerves such as the sural nerve, ulnar nerve, median nerve, and the spinal nerve rootlets.,,, A vasculitic neuropathy has also been proposed but no direct evidence of vasculitic abnormality in the nerve has been observed.
Cranial nerve involvement normally occurs in the presence of increased intracranial pressure, and the direct effect of the tuberculous exudate on the nerve. Though optochiasmatic tuberculoma is well documented, only one case has been reported in which the patient had a tuberculoma involving the trigeminal nerve in Meckel's cave, and two cases have been reported involving the cranial nerves in the cavernous sinus.,,,
In our case, the histopathological examination of the lesion showed the expanded nerve fibres with a multifocal interstitial and perivascular lymphocytic infiltration, along with ill-formed epithelioid cell granulomas associated with a central necrosis suggestive of a tuberculoma. The most probable explanation for the development of this lesion was that the tubercle bacilli would have reached the perineurium through the vasa nervosa and would have elicited periarteritis, following which a granuloma had developed. As this phenomenon is extremely rare, the preoperative diagnosis of tuberculous infection of the nerve complex in the internal acoustic meatus is difficult to establish. In the presented case, the characteristic features of a tuberculoma were not present even on gross inspection of the lesion on MRI. As the histological diagnosis was unexpected, a second opinion on the biopsy was sought, which also confirmed the same diagnosis. In our extensive search, there were no reported cases of intrameatal tuberculoma involving the VII–VIII nerve complex.
Tuberculoma of the central nervous is a very common entity, and has myriad manifestations, often with unusual mode of presentations, especially in countries where tuberculosis is endemic. The extremely rare presentation of a direct cranial nerve involvement should also be considered as one of the manifestations of tuberculous affliction.
We acknowledge Dr. A. V. Shanti (MD, Pathology) for providing us the necessary colored photomicrographs.
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