Diagnoses for gross weakness post c/s arthroplasty?

[StupidZebras]

History: Mid-30s female: C6/7 arthroplasty ~6 mos ago to address L>R UE heaviness > weakness, slight LE weakness, R saddle region numbness.  Positive hoffman's, clonus, weakness (triceps>biceps, L wrist extension, L opposition), and hyperreflexive triceps and patellar DTR. Transient L hypothenar numbness, left lateral brachial burning sensation.

Problem:
Post-op: immediate and significant increase in: all UE and LE weakness (proximal>distal), plus new: decreased sensation L>R LE distal >proximal, transient nerve burn (B lateral brachial, L>R posterior leg and plantar foot), cognitive deficits (executive function, concentration, short-term memory, word finding, multi-tasking), gait changes (crouched, adducted, loss of balance, LE buckling with transfers and stairs), gross saddle region tingling and decreased sensation, delayed ankle balance strategies, fine motor coordination deficits, and extreme fatigue.

Positive exam findings: DTR all UE and LE hyperreflexive B, clonus, hoffman's, weakness ( triceps, biceps, wrist and finger extension, opposition, finger abduction, ankle DF, ankle PF, hamstring, hip flexion, knee extension, 1st toe extension)

Negative workups (MRI -brain, t-spine, c-spine, lumbar, LP labs, dynamic c-spine repeat xrays, c-spine myelogram, blood work, SSERs UE & LE, rheum panels, LE EMG NCV). Slight resolving C8 radiculopathy on EMG L.

Docs are stumped- rec'd seeking out tertiary care center such as Hopkins. Any thoughts on diagnoses, ideas to try, people to see?

Thanks!