In this report, we describe a case of abducens nerve palsy associated with rickettsial infection. The patient initially presented with high-grade fever and was initially diagnosed as having typhoid fever and treated accordingly. The diagnosis of rickettsial infection was initially missed in the absence of typical skin rash. Fundus examination, showing fairly typical superficial retinal infiltrate, led us to suspect rickettsial disease. The diagnosis was confirmed by the positivity of the serologic test for Richettsia Typhi. The patient received a 15-day course of doxycycline therapy, with subsequent favorable response.
MT is frequently misdiagnosed, being a major cause of fever of unknown origin in numerous geographic regions. The initial clinical presentation of MT develops after an 8- to 16-day incubation period, and includes non-specific clinical manifestations, such as high fever, headaches and an often poorly visible maculopapular rash [1, 2]. However, this classic triad was found in only one-third of infected patients [1]. Furthermore, the contact with vectors were rarely mentioned by infected patients and flea bites are occasionally found on physical examination [1]. The clinical course of MT is generally benign and self-limited [1, 2]. Complications are uncommon including pneumonia, renal insufficiency and neurologic involvement [1, 10].
Besides superficial retinitis, an array of other ocular manifestations has been described in association with rickettsial infection including retinal vasculitis, anterior uveitis, optic disc swelling, optic neuropathy, and Parinaud ocular glandular syndrome [2, 3]. Neurologic complications occur in 2–10% of patients with MT, and they include aseptic meningitis, meningoencephalitis and rarely, cranial nerve palsy [1, 10]. There are only a few reported cases of ocular nerve palsy associated with rickettsial disease, mainly involving the third and the six nerve [4–9]. Abducens nerve palsy was associated with meningoencephalitis and/or raised intracranial pressure in the majority of reported cases (Table 1)[5–7]. However, isolated abducens nerve palsy without obvious meningoencephalitis was reported only twice (Table 1) [8, 9]. This could result from microvascular infarction involving the cranial nerve, reflecting the marked tropism of rickettsial organisms for the endothelial cells of small vessels. The latter mechanism could explain the development of abducens nerve palsy in our patient, but a raised intracranial pressure could not be excluded. Therefore, bilateral optic disc swelling in our patient might correspond to papillitis or papilledema.
Table 1
Reported cases of murine typhus related abducens nerve palsy
| Author | Country | Age (years) | Gender | Fever | Headache | Skin rash | Duration of symptoms before onset of ocular nerve palsy | abducens nerve palsy laterality | Associated complications |
| Simon NG, et al. [5] | Australia | 20 | Male | + | + | - | 10 | Bilateral | Seizure, Meningoencephalitis |
| Masalha R, et al. [6] | Israel | 22 | Female | + | + | - | 14 | Right | Mild subacute meningoencephalitis |
| Hsu CH, et al. [8] | Indonesia | 31 | Male | + | + | - | 2 | Right | Liver dysfunction |
| Moy WL, et al. [7] | Singapore | 39 | Male | + | - | - | 9 | Right | Liver dysfunction, Mild meningitis |
| Moy WL, et al. [7] | Indonesia | 27 | Female | + | + | - | 4 | Bilateral | Meningoencephalitis and ventilator associated pneumonia |
| Lin Ting-Yang, et al [9] | Taiwan | 39 | Female | + | + | + | 9 | Left | Liver dysfunction |
| Present case | Tunisia | 18 | Female | + | + | - | 10 | Left | Liver dysfunction |
MT should be considered in the differential diagnosis of abducens nerve palsy in any patient with unexplained fever living in or travelling back from a specific endemic area. Ophthalmic examination, showing typical fundus changes, may be helpful to establish an early diagnosis and to start an appropriate rickettsial treatment.