Altered mental status due to Lyme disease

An 84-year-old man was admitted to the hospital due to an altered mental status. He had a history of stroke and mild to moderate dementia.

According to his wife, he had been having hallucinations 3 to 4 days prior to his hospitalization. And although he suffered from dementia, his symptoms had recently worsened.

Four weeks prior to the onset of symptoms, the man had been vacationing in Maine, a region endemic for Lyme disease.

“Oral intake had diminished considerably and he was found to have decrease in functional capacity,” Chabria wrote. Additionally, the patient was agitated, confused and at times mumbling incoherently.

He did not show any signs of an infection and his white blood cell (WBC) count and temperature were normal.

However, the man had a small bruise on his arm, which his wife attributed to an insect bite, likely a ‘black fly.’ But this could not be confirmed. Therefore, clinicians opted to treat empirically for Lyme disease.

“The presence of an atypical rash which looked more like a bruise prompted the authors to look for possible central nervous system involvement in Lyme disease,” the authors wrote.

An EEG showed diffuse slowing consistent with encephalopathy.

Test results revealed an elevated protein level, and a WBC count of 43/mm3 with 83% mono nuclear cells. Red blood cells were absent.

Based on these findings, the man was treated empirically on IV Ceftriaxone.

“This case illustrates the importance of an index of suspicion for the diagnosis of Lyme involvement of the central nervous system in a patient who at baseline had dementia.”

Testing later revealed he was positive for Lyme disease. And after several days of treatment, his mental status improved.