Cerebral vasculitis and lateral rectus palsy – two rare central nervous system complications of dengue fever: two case reports and review of the literature

An otherwise healthy 53-year-old Singhalese woman who was an office worker from Southern Province, Sri Lanka, presented to a local hospital with an acute febrile illness with no apparent focus of infection. She had no significant past medical illnesses and did not smoke or consume alcohol. Three days prior to her hospital admission, she developed high fever with chills, myalgia, and moderate headache. She was conscious and rational with no hemodynamic compromise. Her full blood count revealed a hemoglobin level of 13.6 g/dl, packed cell volume (PCV) of 37.9%, white blood cell count of 4.2 × 10³/mm³, and platelet count of 105 × 10³/mm³. The result of her nonstructural protein 1 (NS1) antigen test (enzyme-linked immunosorbent assay) was positive. Her liver transaminases were elevated with aspartate aminotransferase (AST) of 161 U/L and alanine aminotransferase (ALT) of 113 U/L. In the next 48 hours, she was observed in the local hospital with serial full blood count measurements, which showed a gradual reduction of her platelet count to 41 × 10³/mm³ on the fifth day of her illness, at which point her PCV had risen to 42%. She had evidence of free fluid in the hepatorenal pouch on an ultrasound scan, indicating progression into the critical phase of DHF. She was observed and managed in the next 48 hours of the critical phase according to the established national guidelines on dengue management [12]. She went through the critical phase without any significant complication, such as bleeding, shock, or multiorgan failure. Following resolution of the critical phase, she was afebrile and clinically improving. Her PCV dropped from 42% to 36.5%, and her platelets showed a gradual increase to 141 × 10³/mm³. However, on postcritical day 1, she experienced acute-onset slurring of speech, deviation of the mouth, difficulty in swallowing, and unsteadiness in gait. At this juncture, she had no fever, headache, or seizures. An urgent noncontrast computed tomographic scan did not demonstrate any particular abnormality in the brain and brainstem. The patient was transferred to our unit for further evaluation and management.

On admission to our unit, the patient was hemodynamically stable with a blood pressure of 112/74 mmHg and pulse rate of 84 beats/minute. She was afebrile but was slightly drowsy with a Glasgow Coma Scale score of 13/15. She had right-sided lower motor-type facial nerve (cranial nerve VII) palsy with ipsilateral palatal weakness, horizontal nystagmus with fast component to the right, and mild weakness in the left upper and lower limbs with normal reflexes and sensory and plantar responses. The rest of the examination, including funduscopy, was unremarkable. Subsequent laboratory investigations, including septic screening with blood culture and mycoplasma serology, serum electrolytes, and liver and renal function, did not reveal any significant abnormalities. Apart from leukopenia (total white cell count of 3400/mm³, 42% neutrophils, 56% lymphocytes), a repeat full blood count showed no significant abnormalities. The diagnosis of dengue infection was reconfirmed by the presence of dengue-specific immunoglobulin G (IgG) and IgM antibodies in serum on day 7 of the patient’s illness (ELISA method). Analysis of the patient’s cerebrospinal fluid (CSF) revealed a normal protein level of 53 g/L, a normal glucose level, and no pleocytosis. An electroencephalogram (EEG) showed features of encephalitis (Fig. 1). Magnetic resonance imaging (MRI) of the brain revealed multiple infarctions involving the pons and medulla regions (Fig. 2).

The patient was treated with intravenous dexamethasone to reduce cerebral inflammation. Supportive measures, including physiotherapy and speech therapy, were initiated. She had gradual but progressive improvement over the next few weeks and had a full functional recovery around 1 month after the illness. CNS vasculitis due to dengue infection was the presumptive diagnosis, based on the clinical presentation of acute onset of focal neurological signs with evidence of brainstem infarction and encephalopathy.

A 57-year-old previously healthy Singhalese woman who was a schoolteacher was admitted to our unit with a history of fever, headache, malaise, nausea, and anorexia of 3 days’ duration. She did not smoke or use alcohol or recreational drugs. On examination, she had a temperature of 39.5 °C and was hemodynamically stable with a pulse rate of 66 beats/minute and blood pressure of 112/66 mmHg with no significant postural drop. The rest of her examination was unremarkable. Her full blood count revealed a total leukocyte count of 4100/mm³ with 42% lymphocytes, hemoglobin of 13.4 g/dl, PCV of 40%, platelet count of 94,000/mm³, and elevated liver transaminases (ALT of 77 U/L and AST of 86 U/L). Dengue infection was confirmed by detection of the NS1 antigen.

The patient was started on treatment for uncomplicated dengue fever. However, on the second day of her hospital admission, she started complaining of bilateral diplopia, which worsened upon left gaze. She did not complain of headache, and her consciousness level was not reduced at this stage. An ocular examination revealed a convergent squint in the left eye with evidence of isolated lateral rectus weakness. The results of the rest of the CNS examination, including the vision and fundus of both eyes, were normal. The patient was investigated with an MRI scan of the brain, which ruled out a space-occupying lesion or any other significant pathology. During the patient’s hospital stay, her platelet count dropped gradually to 44,000/mm³ on the fifth day of fever, before it started to rise. Apart from isolated lateral rectus weakness, she did not develop any other complications, such as plasma leakage, shock, hemorrhage, or liver failure.

She was managed with intravenous and oral fluids according to the national guideline for the management of dengue fever [12]. She recovered from dengue fever and was discharged from the hospital on day 7 of her illness. She had evidence of improvement of her lateral rectus palsy at the time of discharge, and it completely resolved within 4 weeks without any specific treatment.