Medical expenses are considered personal expenses. As such, medical expenses are deductible by the spouse that pays the medical expenses. If the medical expenses were paid from community funds (like from a joint bank account) the expenses should be divided equally between the spouses.
See the following from IRS Publication 555:
Personal expenses.
Expenses that are paid out of separate funds, such as medical expenses, are deductible by the spouse who pays them. If these expenses are paid from community funds, divide the deduction equally between you and your spouse.