What Happens if Botox Course is Not Followed?

Botox relaxes muscles. Once the effect wears off, you go back to where you were, since the muscle regains it's original strength. If you repeat the treatments before the Botox fully wears off, the muscles may get thinner (atrophy) and you may have even longer periods between needing injection and then the muscle may not be as strong.
The concept that people "need" Botox once they have one treatment doesn't have to do with worse wrinkles when it wears off, it has to do with the fact that they love what it does for them and want to maintain that look.

Dear Vydi
Of course your wrinkles are going to look worse. But it won't be the results of the BOTOX. No it will be your mind and the effects of time. Think about it this way. For 4 or 5 months you looked great. You have had relief from lines that were enough of an issue that you decided to have BOTOX. Now the treatment has worn off. You brain is designed to compare things and it will not remember how you looked before BOTOX. Instead the comparison will be the old lines versus what you looked like with BOTOX. And of course you will be 6 months older.

If you are not going to maintain your appearance with BOTOX, does it make sense to get BOTOX. Absolutely. Many people do this to look good for an important occasion.

No, you won't look worse if you don't continue Botox, but you may THINK you look worse because after having the softening effect from Botox, you will be used to the new way you looked while it was in effect.
A number of patients find that several timed injections of Botox will actually help their muscles stay more relaxed. Most of the facial frowns and squints we make are habitual. By interfering with that habit, you've stopped the progression of deeper wrinkling or lines, so you have, in a fashion, slowed down the process of wrinkle and line formation.

The good news is that your wrinkles are not worse if you stop using Botox. The bad news is that they will bother you more, because you know how much better you look with Botox.
There's more good news, too... If you don't use Botox at all, your wrinkles get worse over time from bunching up the skin with smiles and frowns. While you are using Botox, your wrinkles don't get worse. You prevent the formation of new wrinkles. So if you use Botox for awhile, even if you stop, your skin has less wrinkles than it would have.

Failure to continue with Botox after a single treatment will not cause wrinkles to look worse than before treatment.  The wrinkles will probably revert to their pretreatment appearance.  After several treatments, the muscles causing wrinkles sometimes weaken and results last longer.

 The fact of having Botox once will relax the muscles during that 3-4 month period. Thus, people who have undergone Botox should have slightly less depth to their lines than those who did not. 
    The wrinkles certainly should not look worse if Botox is not repeated.