Is Hyperpigmentation a Side Effect of Accutane?

Without examining you and getting a complete history, it is hard to say what caused the hyperpigmentation.  As you describe it as being along the hair line, I wonder if you have seborrheic dermatitis (dandruff).  Many times if presents as scaling, redness, or discoloration (darker or lighter) along the hair line (usually frontal).  By itself, Accutane is not a common cause ot this type of hyperpigmentation.  I recommend that you discuss this with your dermatologist.

Having been on accutane, you are more prone to the damaging effects of the sun which include sunburn, but also hyperpigmentation called melasma. I would start wearing an SPF 60 sunscreen, and add a topical hydroquinone (e.g. ultraquin, lustra) to bleach out the darkened skin. If things aren't better in 2-3 months, see a dermatologist for a "modified Kligman's formulation" and/or chemical peeling. Good luck!