One-and-a-half syndrome is a syndrome characterized by horizontal movement disorders of the eyeballs, which was first reported and named by Fisher in 1967. It presents a combination of ipsilateral conjugate horizontal gaze palsy (one) and ipsilateral internuclear ophthalmoplegia (INO) (a half). On the basis of the one-and-a-half syndrome, there are a series of related rare syndromes called the one-and-a-half syndrome spectrum disorders. This article reviews rare cases of one-and-a-half syndrome spectrum disorder, describes the clinical and pathological features of different syndromes, and summarizes their nomenclature. Quant Imaging Med Surg 2017;7(6):691-697 qims.amegroups.com Xue et al. One-and-a-half syndrome with its spectrum disorders horizontal conjugate movement of eyes. If the isolated side of PPRF is damaged, the eyes could not gaze at the lesion side, presenting the horizontal gaze palsy to the lesion side (6).The abducens nucleus is located in colliculus facialis, which is in the lower part of the pons and the bottom of the fourth ventricle (7). It contains two functionally distinct cell groups: the abducens motoneurons that innervate the lateral rectus muscle; the internuclear neurons which axons cross the midline and ascend via the contralateral MLF to oculomotor subnucleus and control the medial rectus (8). Therefore, the unilateral lesion of the abducens nucleus will also produce ipsilateral horizontal gaze paralysis.MLF are the longitudinal nerve fibers that locate on the back of the pons and are close to the front of the fourth ventricle, a part of which relating to horizontal gaze is from the side of the abducens nucleus to the contralateral oculomotor subnucleus (9). The lesion of unilateral pontine tegmentum can damage the ipsilateral MLF, causing the ipsilateral INO, and its clinical manifestations show the ipsilateral intraocular muscle paralysis and contralateral horizontal nystagmus when staring at the opposite side. If the damage does not involve the midbrain, the convergence reflex is integrated (10). One-and-a-half syndromeThe one-and-a-half syndrome is caused by a lesion of unilateral tegmentum of pons, causing damage to the PPRF (or abducens nucleus) and MLF ( Figure 2). The most common cause of one-and-a-half syndrome was cerebrovascular disease, and usually was brain stem lacunar infarction, followed by the demyelinating etiology (multiple sclerosis), and then the infectious cause including neurocysticercosis and brainstem encephalitis. Other uncommon causes were head trauma, brain stem tumor (primary or metastasis), astrocytomas, etc. (6,11). Therefore, the vast majority of one-and-a-half syndrome companied by other positioning signs is due to the different lesions of brainstem (3). Only a very small number of patients showed isolated one-and-a half syndrome, while the lesions are smaller and localized, such as brainstem cysticercosis, brainstem tuberculosis, brainstem cavernous hemangioma and the local hemorrhagic infarction of brainstem (12-15).We recently diagnosed a ...

This study provides Class I evidence that for people with PDPH, IV aminophylline reduces headache severity.