When she arrived at the Capitol last week after a more than two-month absence recovering from shingles, Senator Dianne Feinstein, Democrat of California, 89, appeared shockingly diminished.
Ms. Feinstein’s frail appearance was a result of several complications after she was hospitalized for shingles in February, some of which she has not publicly disclosed.
The shingles spread to her face and neck, causing vision and balance impairments and facial paralysis known as Ramsay Hunt syndrome.
Characterized by swelling of the brain, post-shingles encephalitis can leave patients with lasting memory or language problems, sleep disorders, bouts of confusion, mood disorders, headaches and difficulties walking.
And even before this latest illness, Ms. Feinstein had already suffered substantial memory issues that had raised questions about her mental capacity.