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Brain Sciences Nov 2021Parinaud's syndrome involves dysfunction of the structures of the dorsal midbrain. We investigated the pathophysiology related to the signs and symptoms to better... (Review)
Review
Parinaud's syndrome involves dysfunction of the structures of the dorsal midbrain. We investigated the pathophysiology related to the signs and symptoms to better understand the symptoms of Parinaud's syndrome: diplopia, blurred vision, visual field defects, ptosis, squint, and ataxia, and Parinaud's main signs of upward gaze paralysis, upper eyelid retraction, convergence retraction nystagmus (CRN), and pseudo-Argyll Robertson pupils. In upward gaze palsy, three structures are disrupted: the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), interstitial nucleus of Cajal (iNC), and the posterior commissure. In CRN, there is a continuous discharge of the medial rectus muscle because of the lack of inhibition of supranuclear fibers. In Collier's sign, the posterior commissure and the iNC are mainly involved. In the vicinity of the iNC, there are two essential groups of cells, the M-group cells and central caudal nuclear (CCN) group cells, which are important for vertical gaze, and eyelid control. Overstimulation of the M group of cells and increased firing rate of the CCN group causing eyelid retraction. External compression of the posterior commissure, and pretectal area causes pseudo-Argyll Robertson pupils. Pseudo-Argyll Robertson pupils constrict to accommodation and have a slight response to light (miosis) as opposed to Argyll Robertson pupils were there is no response to a light stimulus. In Parinaud's syndrome patients conserve a slight response to light because an additional pathway to a pupillary light response that involves attention to a conscious bright/dark stimulus. Diplopia is mainly due to involvement of the trochlear nerve (IVth cranial nerve. Blurry vision is related to accommodation problems, while the visual field defects are a consequence of chronic papilledema that causes optic neuropathy. Ptosis in Parinaud's syndrome is caused by damage to the oculomotor nerve, mainly the levator palpebrae portion. We did not find a reasonable explanation for squint. Finally, ataxia is caused by compression of the superior cerebellar peduncle.
PubMed: 34827468
DOI: 10.3390/brainsci11111469 -
Journal of Neurological Surgery. Part... Aug 2020The orbit is a paired, transversely oval, and cone-shaped osseous cavity bounded and formed by the anterior and middle cranial base as well as the viscerocranium. Its...
The orbit is a paired, transversely oval, and cone-shaped osseous cavity bounded and formed by the anterior and middle cranial base as well as the viscerocranium. Its main contents are the anterior part of the visual system, globe and optic nerve, and the associated neural, vascular, muscular, glandular, and ligamentous structures required for oculomotion, lacrimation, accommodation, and sensation. A complex stream of afferent and efferent information passes through the orbit, which necessitates a direct communication with the anterior and middle cranial fossae, the pterygopalatine and infratemporal fossae, as well as the aerated adjacent frontal, sphenoidal, and maxillary sinuses and the nasal cavity. This article provides a detailed illustration and description of the microsurgical anatomy of the orbit, with a focus on the intrinsically complex spatial relationships around the annular tendon and the superior orbital fissure, the transition from cavernous sinus to the orbital apex. Sparse reference will be made to surgical approaches, their indications or limitations, since they are addressed elsewhere in this special issue. Instead, an attempt has been made to highlight anatomical structures and elucidate concepts most relevant to safe and effective transcranial, transfacial, transorbital, or transnasal surgery of orbital, periorbital, and skull base pathologies.
PubMed: 33072474
DOI: 10.1055/s-0040-1715096