[Arachnoid cyst and tension headache: symptom or accidental finding?]

We report a 34 year old male patient presenting with occipital headache and bilateral shoulder and neck pain. Cranial MRT discloses a large arachnoid cyst ventral to the medulla oblongata. The cyst displaces the caudal medulla oblongata dorsally to an angle of almost 90 degrees without causing myelopathy. Physical examination reveals normal neurological findings without any sign of brainstem lesions or lesions of the medulla oblongata. Orthopedic evaluation shows mild functional abnormalities as expected in tension headache. Multiple electrophysiologic investigations such as motor-, somatosensory-, and acoustic-evoked potentials, masseter and brain stem reflexes, and electromyography of the left M. trapezius were performed and reveal normal results. MR-angiography discloses displacement of the left vertebral artery to the right without stenosis.We discuss the possibility of a causal connection between the cystic lesion and the reported symptoms. Considering the findings based on a review of the available literature we conclude that the pain syndrome is very likely unrelated to the arachnoid cyst. The latter is herewith an accidental finding in a patient with tension headache, and underlines the importance of thoroughfull clinical examination to avoid unnecessary diagnostic or therapeutic procedures.