“…Upon literature review, the most common causes of HFS, besides neurovascular compression, were cerebellopontine angle tumors (epidermoid, arachnoid cyst, lipoma, and vestibular schwannoma) 2 , 3 , 9 , 15 , 26 , 38) , and other unusual causes including cerebellopontine angle medullary venous malformations 15 , 24) , Paget's disease 16 , 25) , occipital falcine meningioma 5) , cerebellopontine angle meningioma 11) , acoustic schwannoma 11) , pontine glioma 45) , fourth ventricle ganglioglioma 6) , pontine infarction 43) , syringobulbia 4) , multiple sclerosis 42) , trauma 29) , hypothyroidism 13) , idiopathic intracranial hypertension 37) , vertebrobasilar ectasia 21) , craniovertebral anomalies 28) , glomus jugular tumor 23) , parotid gland 8 , 11 , 12 , 32) , and arterial hypertension 33) . A few cases of HFS alone or in combination with trigeminal neuralgia have been reported as a false localizing sign in patients who had a contralateral posterior fossa mass or acoustic neuroma 30 , 31) .…”