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. The virus also brought on a previously unreported case of encephalitis, a rare but potentially debilitating complication of shingles, according to two people familiar with the senator’s diagnosis who spoke on the condition of anonymity to describe it.

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. Older patients tend to have the most trouble recovering. And even before this latest illness, Ms. Feinstein had already suffered substantial memory issues that had raised questions about her mental capacity.

The grim tableau of her re-emergence on Capitol Hill laid bare a bleak reality known to virtually everyone who has come into contact with her in recent days: She was far from ready to return to work when she did, and she is now struggling to function in a job that demands long days, near-constant engagement on an array of crucial policy issues and high-stakes decision-making.

[This seems to fit the stories and images of her return this week, but I still find it interesting that so many media outlets are focused on Feinstein while ignoring the clear “diminishment” of John Fetterman. The Washington Post got caught this week rewriting its reporting to cover up Fetterman’s incoherence, for instance, while the NYT never mentioned it at all. This seems like a narrative with a purpose — a way to pressure Feinstein into resigning so that Gavin Newsom can pick a winner ahead of the primary for this seat next year. — Ed]