My youngest sister had Lyme Disease in the late 1990s. Very, very ugly disease. She had Bell's Palsy in conjunction with the Lymes. It took months and months to get a diagnosis. She wore a continuous IV for a long time. The medicine it took to arrest the disease is literally poison.
She still suffers lingering effects.
We call it Lyme’s Fog. The people we know who have a relapsing/remitting form of it do suffer long term cognitive deficit.