Millard-Gubler syndrome (MGS), also known as facial abducens hemiplegia syndrome or the ventral pontine syndrome, is an eponym after two French physicians Auguste Louis Jules Millard and Adolphe-Marie Gubler in 1858 who first described the features of this syndrome. MGS is one of the classical crossed brainstem syndromes characterized by a unilateral lesion of basal portion of the caudal pons involving fascicles of abducens (VI) and the facial (VII) cranial nerve, and the pyramidal tract fibers.
Components of MGS
MGS often presents with other neurological deficits such as contralateral hemiparesthesia and contralateral cerebellar ataxia as many other nuclei fibers exist near the root fibers of the facial nerve nucleus.
Causes of Millard-Gubler syndrome (MGS) vary with age. In younger people, the leading causes are tumors, infectious diseases (neurocysticercosis and tuberculosis), demyelinating diseases (multiple sclerosis), and viral infection (Rhomb encephalitis). In older patients, it is most frequently caused by vascular events such as hemorrhage and ischemia (secondary to stenosis of the basilar artery) or due to compression of the arteries by prepontine subarachnoid hematoma. There have been some reported cases of MGS due to aneurysm of the basilar artery.
Epidemiology varies according to the cause of the disease.
This syndrome is caused due to a lesion at ventral part of the pons that involves the fibers of cranial nerves VI, VII, and corticospinal tract fibers. Corticospinal and corticobulbar tracts are in the central region of the ventral pons. The medial lemniscus lies posteriorly on each side of the median raphe. Nuclei of abducens (VI) and facial (VII) nerves are found in a dorsal portion of the pons, and their fibers pass through the pontine tegmentum and emerge anteriorly at the cerebellopontine angle. The spinothalamic tract is located in the anteromedial tegmentum, medial to the descending tract and nucleus of trigeminal (V) nerve. MGS lesion involves the ventromedial part of the pons which contains the corticospinal tract and fascicular intrapontine portion of the VII nerve, causing ipsilateral paralysis of the facial nerve and contralateral hemiplegia. Classical cases of MGS sometimes involve fibers of the VI nerve. The medial lemniscus and spinothalamic tract are typically spared in this syndrome, thus explaining the absence of the sensory symptoms.
Symptoms and Signs
The diagnosis of Millard-Gubler syndrome (MGS) is confirmed by a clinical examination of VI and VIII CN along with hemiplegia of upper and lower extremities. Because various etiologies might cause MGS, take a detailed history to exclude other causes like infection (fever) or vascular insult (presence of other neurologic deficits).
Neurological Imaging, i.e., computed tomography (CT) and magnetic resonance imaging (MRI) are helpful in identifying the lesion. However, MRI of the brain is more sensitive and specific than CT scan to identify the infarcts at an early stage of onset, especially in the setting of small pontine lesions. Ischemic stroke of pons on CT brain shows a hypodense lesion in the anteromedial side of the pons. MRI brain shows a lesion in one side of the anteromedial pons, which is hypointense on T1 sequences and hyperintense on T2 /FLAIR sequences. The Magnetic resonance imaging also shows diffusion restriction in the pontine ischemic lesion. However, there have been some reported cases presenting as MGS with no imaging findings. Other associated lesions (tuberculoma, tumors, and cysticercus granulomas) can also be identified using imaging.
Vertebral angiography is helpful in cases if the lesion is caused due to the occlusion of the basilar artery.
Pontine-crossed syndromes are Foville, Raymond, Raymond–Cestan syndrome, Gasperini syndrome, and Brissaud-Sicard syndrome. These syndromes are unique as the lesion involves the brainstem above the decussation of the pyramidal tracts. Therefore, the clinical signs of the cranial nerve are ipsilateral to the lesion, and the long tract signs contralateral, resulting in crossed syndrome.
Treatment mainly depends on the etiology of the disease. In some cases, patients presenting with multiple deficits require early conservative measures together with multidisciplinary rehabilitation.
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