Benedict syndrome (BS), also termed paramedian midbrain syndrome, is a rare stroke manifestation involving a lesion of the tegmentum of the midbrain. Infarctions of the red nucleus, cerebral peduncle, oculomotor fascicles, and the lower oculomotor nucleus are most commonly observed. BS manifestation is normally a consequence of infarcted branches of the posterior cerebral artery. BS is closely related to Weber's syndrome and Claude's syndrome.
Benedict syndrome (BS) is caused by a stroke in the midbrain and usually presents as an ipsilateral oculomotor nerve palsy with contralateral hemi-tremor. Most common symptoms in BS are impaired eye movements affecting only one eye, hemichorea, slow one-sided tremor in the limbs, contralateral ataxia, dilated unresponsive pupils, ptosis, diplopia, hyperactive tendon reflexes, adiadokokinesis, contralateral hyperaesthesia and contralateral hemiparesis [1] [2] [3]. BS manifests with symptoms reminiscent of Weber's syndrome (WS) and Claude's syndrome (CS). BS is more often associated with hemiataxia, i.e. incoordination of movements, while WS more often presents with paralysis symptoms. An identifying symptom for BS in comparison to CS is contralateral hemiparesis, which never occurs in CS. Patients with BS have a rhythmic tremor of the contralateral hand and foot, which intensifies as a consequence of emotional excitement and during voluntary movements. Tremor is always absent during sleep in BS patients [4] [5].
BS is caused by a lesion, i.e. an infarction, hemorrhage or a tumor in the tegmentum of the midbrain and cerebellum. Infarctions of the posterior cerebral artery are suspected to be conducive to BS in most reported cases. Tuberculosis can also cause BS. Disruptions in the third cranial nerve, the red nucleus, the corticospinal tracts, the brachium conjunctivum, and the superior cerebellar peduncle decussation are normally associated with BS manifestations [1].
Motor anomalies in BS patients include a loss in arm swing on the affected side while the patient walks, a permanently semi-flexed arm and uncoordinated walking steps. These steps are characterized by swinging legs and a quick foot drop [4].
Cognitive functions remain unaffected in BS patients [1] [6].
Diagnosis of BS relies on a confirming the patient's stroke risk factors, on clinical investigations and on brain imaging studies. In selected cases with a possible connection to a tuberculosis infection, an analysis of cerebrospinal fluid is also necessary [1].
A patient history featuring a smoking habit, pronounced hypertension, prolonged untreated diabetes, hypercholesterolemia and a familial predisposition for stroke-related disorders are crucial parameters for the diagnosis [7][8].
Clinical examination should focus on obvious BS symptoms like ptosis, eye deviations, pupillary anomalies, contralateral hemiparesis, lack of voluntary motor coordination and tremors. Eye deviations occur because of an injury to the oculomotor nerve and force the eyes outward or downward [1].
Magnetic resonance imaging (MRI) and computer tomography (CT) scans are the final step in the workup since these methods provide the best chance to exclude other ailments with similar symptoms, e.g. cavernous sinus thrombosis. Both methods can detect disruptions in the above-mentioned midbrain areas [1] [9].
Deep brain stimulation may provide a valuable treatment option for the BS associated intention tremor [10].