hey there T, have not experienced it myself but it's a cognitive symptom called emotional lability. i saw a figure of around 20% of ms patients deal with this one. it can happen to people with other brain injury as well. it is also seen in stroke, ALS, etc.
if you want to read up here are some terms you could use to search google scholar for studies: pseudobulbar affect, pathological laughter and crying, emotional lability, emotionalism, emotional dysregulation, or, more recently, involuntary emotional expression disorder (IEED).
i always focus on nutrition and there are lots of common nutritional problems in ms patients. on emotional lability, in regular google, iron, magnesium and b-vitamins are coming up. those all make sense but i was thinking 'where's the zinc and PUFA?'. using google scholar, zinc is the first result.
http://jn.nutrition.org/content/130/2/361.full.pdf
Zn and behavior in adults
"There have been four experimental studies of Zn intakes or status and behavior in adult humans. Henkin et al. (1975) reported increased emotional lability and perceptual and memory deficits in patients with progressive systemic sclerosis after administration of histidine, a Zn chelating agent."
and the PUFA
http://www.bioriginal.com/services/files/file_41.pdf
from
http://www.ncbi.nlm.nih.gov/pubmed/11817499
"A three-month clinical trial in children with specific learning problems, mainly dyslexia along with ADHD features, examined the effect of taking EPA and DHA from fish oil combined with GLA from evening primrose oil, compared to an olive oil placebo. The treated group demonstrated
improvements in cognitive function, hyperactivity, opposition, psychosomatic symptoms, social problems, restlessness, impulsiveness,
emotional lability and inattention. No improvements were noted with the placebo group"
b-complex, mag, zinc, omegas, these are all nutrients that come up often related to MS. or any other cognitive issue. my old roomie was dealing with bipolar disorder and while she lived with me she stopped having episodes. she would complain about feeling such and such a way, i would say have you been taking _________? (fill in blank pertaining to whichever symptom) and she would say oh i ran out of that a while ago. so she would re-stock and her symptom would resolve. important ones for her were the b-complex, magnesium, and fish oil. i probably had her on zinc too for good measure
so all that said, if i may ask, what's your diet like? do you have a supplement regimen? if so, what are you already taking daily?