Neurobrucellosis complicated by sensorineural hearing loss: about a case

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Brucellosis is one of the most common zoonotic infections in the world [1]. It is an endemic disease in Saudi Arabia. [2]. Although the disease is present worldwide, the Mediterranean region, the Middle East, Africa and Latin America are the main areas of public health concern. [2]. Brucellosis infects more than 500,000 people in sub-Saharan Africa each year, study finds [2]. It is caused by Brucella, a gram-negative, nonmotile, nonspore-forming coccobacillus and facultative intracellular organism [3]. There are approximately 12 species of Brucella, and the most common species causing brucellosis worldwide are Brucella melitensis (from sheep and goats), Brucella abortus (from cows) and Brucella canis (from dogs). ). [2].

Most infections are transmitted to the human population through direct contact with fluids from infected animals and consumption of their food products, including unpasteurized milk and cheese. [3]. In addition, occupational or recreational exposure to infected animals and their products, such as breeders or veterinarians, may increase the risk of brucellosis. [1]. There is also evidence of mother-to-child transmission via breastfeeding [4].

Brucellosis is a multisystem infection that affects any organ in the body. Neurobrucellosis (NB) is the most serious but rare complication of brucellosis. It can involve the central and peripheral nervous systems, with a prevalence of 1.7% to 10% of brucellosis worldwide [5]. This study aimed to describe a case of NB with a history of progressive bilateral deafness.

This case was reviewed by biomedical ethics and an exemption was received. A 35-year-old man with no medical illness was referred to our institution complaining of rapidly progressive bilateral hearing loss for 18 months. It is associated with recurrent episodes of fever, sweating, fatigue and difficulty walking. He also suffered from headaches, back pain and joint pain. He had no history of otorrhea, tinnitus, vertigo, weight loss, reduced appetite, or history of exposure to ototoxic drugs or noise trauma. He had a history of consuming raw cheese and milk in Yemen three years ago for about two years. On examination, the patient was conscious and alert, but had severe bilateral hearing loss. His body weight was 50 kg, his height was 160 cm and his vital signs were within normal limits.

On neurological examination, the power of the lower limbs was rated 4/5 with normal tone. Symmetrically sharp deep tendon reflexes of the upper and lower limbs with a positive Babinski sign on the right side. Sensory examination results were normal. The gait was normal. Cranial nerve examination revealed bilateral sensory neural deafness. All other cranial nerves were normal. Meningeal signs were negative. His cardiovascular and respiratory systems were unremarkable. Pure tone audiometry revealed bilateral profound sensorineural hearing loss (SNHL) with bilateral type A tympanograms (Figure 1).

Magnetic resonance imaging (MRI) was performed and leptomeningeal enhancement of the perimesencephalic and cervical spinal cord, as well as enhancement of the cranial nerves, were observed (Figure 2).

MRI-brain-scan-with-contrast-showing-the-meningeal-perimesencephalic-and-cervical-enhancement-of-the-spinal-cord-as well-as-the-enhancement-of-the-cranial-nerves

Brucellosis screening test showed positive for Brucella antibody with a titer of 340 (normal range

The patient was admitted to hospital with a case of neurobrucellosis (NB) based on lumbar puncture (LP) analysis. The medical and infectious disease teams treated the patient with intravenous doxycycline, rifampin and ceftriaxone for six weeks. After six weeks, her symptoms, including fever, night sweats, fatigue and difficulty walking, improved, but her repeated audiogram remained unchanged. After nine months, multiple audiograms and auditory brainstem response (ABR) testing showed deep and persistent bilateral SNHL (Figure 1). The patient was then referred to the cochlear implant program for cochlear implantation.

Brucellosis is considered a major health problem in Middle Eastern countries, including Saudi Arabia. It is the most common zoonotic infection in the world [2]. However, the disease is highly neglected by the World Health Organization (WHO) and the World Organization for Animal Health (OIE) [6,7]. It is endemic to Saudi Arabia, with an infection rate of around 70 per 100,000 people [2,8]. We reviewed several studies conducted in various regions of Saudi Arabia. Human brucellosis is considered one of the most frequently reported cases, especially in Riyadh [1]. In the southern region of Saudi Arabia, a study was conducted with 4,900 patients; 2.3% had active disease and 19.2% had serological evidence of exposure to brucella antigen [1]. While in a study of 1733 patients conducted in Riyadh, the prevalence of brucellosis was 8.8% [1]. The main causative factors in this region are the consumption of unpasteurized raw milk and the interaction with contaminated animals due to the common practice of drinking raw milk mainly from sheep and camels. [9,10].

There is no consensus on the exact diagnosis of NB as it has neither a conventional clinical picture nor clear findings in CSF [11,12]. Thus, the diagnostic criteria proposed in the literature [5,13,14] are the following:

1) The presence of clinical symptoms consistent with either meningitis or meningoencephalitis

2) Consistency of typical CSF findings with meningitis (protein concentrations > 50 mg/dL, leukocytes > 10/mm3 and glucose/glycemia ratios

3) Positive results of bacterial culture or serological test for brucellosis in blood samples (positive test for Rose Bengal and agglutination in serum tube with titer ≥ 1/160), CSF (positive test for Rose Bengal or agglutination in serum tube with any titer), or positive bone marrow culture

4) Findings of Cranial Computed Tomography (CT) or Magnetic Resonance Imaging (MRI)

Brucellosis has a variable clinical appearance due to its widespread systemic involvement during contamination. Central nervous system (CNS) involvement is a rare but serious complication of disease progression. It can often be the only sign of human brucellosis, with a prevalence of 1.7% to 10% worldwide [5]. Meningitis, which can be acute or chronic, is the most common presentation in NB, accounting for 17% to 74% of all cases. Other neurological manifestations include encephalitis, meningoencephalitis, radiculitis, myelitis, peripheral and cranial neuropathies, subarachnoid hemorrhage, psychiatric manifestations, brain abscesses and demyelinating syndrome. [12,15].

Cranial nerve (CN) involvement is common in brucellosis, particularly in the sixth, seventh, and eighth CN. The acoustic nerve has been identified as the most frequently affected cranial nerve [16,17]. When Brucella toxin enters the labyrinth, it affects the cochlear system, causing damage and hearing loss [18]. According to Thoma et al., there is no adequate documentation of cases of sensorineural hearing loss in New Brunswick. Therefore, otolaryngologists were not aware of this [18]. In NB, SNHL is usually bilateral and primarily affects high frequencies, and our patient had deep bilateral SNHL affecting all frequencies.

In NB, rifampicin, doxycycline and trimethoprim/sulfamethoxazole are effective for long periods. These chemotherapeutic agents penetrate the central nervous system and exert synergistic effects. Ceftriaxone can be added as a fourth agent to this protocol [19,20]. Our patient received doxycycline, rifampicin and ceftriaxone for six weeks.

Brucellosis-induced CN paralysis usually improves with no residual effects after administration of antibiotics [21]. Chronic CNS infections, on the other hand, often result in permanent neurological deficits. In our patient, after six weeks of antibiotic therapy, the audiograms remained unchanged and contradicted the case report of Thomas et al. [18], who had a one-year history of bilateral high-frequency SNHL and received tetracycline and rifampicin for a total of six weeks with no improvement in hearing. In contrast, CN paralysis completely improved after treatment, according to Ucmak et al. [22].

There are only sporadic reports of SNHL as a complication of NB. One of the first reports was that of Bucher et al. [23], who diagnosed SNHL in a patient with severe chronic NB. Subsequently, Thomas et al. [18]Bedur et al. [24]Cagatay et al. [25]and Sengoz et al. [26] all reported similar results in NB patients developing SNHL. Interestingly, all reported cases (including our case) had suffered from ataxia and gate-related issues in addition to SNHL, indicating cerebellar involvement [18,23-26].

Therefore, prevention is an essential aspect of disease control and vector management is crucial when dealing with zoonotic infections. Pasteurization of milk and safe handling of raw meat are essential preventative measures. In addition, animals should be checked and vaccinated regularly. Finally, an educational program for healthcare workers and veterinarians and livestock owners should be considered. [1,2].

Otorhinolaryngologists should not overlook NB as a cause of hearing loss. It should be sought in any patient with hearing loss, particularly when other differential diagnoses have been ruled out or if the usual or demographic history puts the patient at higher risk of contracting NB.

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