Mom has had MS for decades and recently diagnosed with scoliosis. She
is considering "spinal fusion" surgery to reverse/correct the
scoliosis. It is apparently rare/unheard of for those with multiple
sclerosis to receive this type of surgery; is there research for or
against this procedure for a patient already dealing with MS?

2.What is the expected recovery period. (She already walks with a
walker; will this make it harder or easier for her to walk)?

To my knowledge,
There is only 1 paper with 5 MS cases underwent spine fusion in 1994 at Mayo.
Unfortunately, electronic version of the paper is not available. Hope
this helps reassure you that it should not be that risky for your mom
to undergo the surgery.
Thira Woratanarat MD, MMedSc, DHFM
Thailand

1: Spine. 1994 Feb 1;19(3):323-8.  
Transthoracic disc excision and fusion for herniated thoracic
discs.Currier BL, Eismont FJ, Green BA.
Department of Orthopedics, Mayo Clinic, Rochester, Minnesota.

Transthoracic discectomy and fusion were performed on 19 patients for
a central or central-lateral herniated thoracic disc. At initial
visit, 14 patients had evidence of myelopathy, 5 had bowel or bladder
dysfunction, and 13 had pain. Previous laminectomy in three patients
compromised the result of later anterior decompression. Coexistent
multiple sclerosis was diagnosed in two patients, who had an atypical
postoperative course. The overall results of transthoracic discectomy
and fusion in patients without prior laminectomy or coexistent
multiple sclerosis were excellent in six, good in six, fair in one,
and poor in one, demonstrating that it is a safe and effective
procedure.

PMID: 8171365 [PubMed - indexed for MEDLINE]