Do you recommend lumbar puncture for suspected early GBS without motor involvement?

If purely for the confirmation of a GBS diagnosis, then no.

CSF testing has limited utility for Guillain-Barré syndrome (GBS) diagnosis early in the disease course. Cytoalbuminologic dissociation is only present in 50% of patients in the first four days and rises to ~80% after the first week (Al-Hakem et al., PMID 37076309). By and large, the utility of most diagnostic testing for GBS is for identifying mimics (e.g., carcinomatosis, West Nile disease, transverse myelitis) rather than concluding t...