Hi
Welcome to the MedHelp forum!
Neck lymph nodes can be the result of tonsillitis, pharyngitis (infection of upper throat), infection in mouth, caries in tooth, internal ear infection, outer ear infection, eczema, dermatitis, dandruff, breast cancer, fungal infection, other cancers like lymphoma etc. If your friend had flu like symptoms initially then it could be due to infectious mononucleosis too.
The enumerated the possibilities can be investigated or ruled out one by one by your physician, ENT and dentist. Take care!
Has he been to see an ENT yet if not I'd suggest having a Caloric testing done,
like for example has any of this occurred before he started having vertigo and swollen lymphnodes :
Did he ever have any noise trauma, or physical trauma to his head or ear?
Does he swim/dive a lot?
Any sinus problems before this happened, Severe sinus problems?
my sister had perilymph fistula on ONE ear. you can get them spontaneous as well, and there is also a possibility of it developing from a problem with the bone(marrow)...but very rare. if he had sneezed or blew his nose "the wrong way" it could have had enough pressure to damage the membrane.
A caloric testing they do water into your ear canal while your eyes are monitored by a camera for nystagmus (twitchy motions) and you are in the dark.
If any of that applies to him, have him go get the caloric testing and if that is the case he might have to have cranial surgery.