Parinaud’s syndrome (pronounced ‘Parinò syndrome’) is a neurological disorder caused by a lesion in the roof of the midbrain, resulting in the inability to move the eyes up and down

Parinaud syndrome belongs to the group of eye movement abnormalities and pupil dysfunctions and – together with Weber syndrome, superior cerebellar artery syndrome, Benedikt syndrome, Nielsen syndrome and Nothnagel syndrome – is one of the alternate midbrain syndromes. Parinaud’s syndrome is also called ‘sun-setting syndrome’ but should be distinguished from sundown syndrome.

Parinaud syndrome is named after the French physician Henri Parinaud (1844-1905), who first described it in the second half of the 19th century. Parinaud is considered the father of French ophthalmology.

Denominations of Parinaud’s syndrome

Parinaud’s syndrome is also called dorsal midbrain syndrome, setting sun syndrome or, by extension, setting sun phenomenon, setting sun sign or waning sun sign.

In English it is called dorsal midbrain syndrome, vertical gaze palsy, upward gaze palzy, sunset sign, setting-sun sign, sun-setting sign, sun-setting syndrome, sunset eye sign or setting-sun phenomenon.

Epidemiology of Parinaud’s syndrome

The disease is most prevalent among young patients with brain tumours in the pineal gland or midbrain: pinealomas (intracranial gernomas) are the most common lesion producing this syndrome.

The disease is also common among women in their 20s and 30s with multiple sclerosis Another category that is most often affected by Parinaud’s syndrome are older patients following an upper brainstem stroke.

Causes of Parinaud’s syndrome

Parinaud’s syndrome is caused by a lesion, either direct (e.g. ischaemic damage) or indirect (e.g. compression) to the roof of the midbrain (the upper part of the brainstem), in particular by compression of the vertical gaze centre in the rostral interstitial nucleus of the medial longitudinal fasciculus, including the superior colliculus adjacent to the oculomotor (origin of cranial nerve III) and the Edinger-Westphal nuclei.

Due to this lesion, the eyes lose the ability to move upwards and downwards.

This lesion can be caused by:

• ischaemic or haemorrhagic cerebral stroke,
• mid-brain haemorrhage,
• neoplasms affecting the lamina quadrigemina,
• pinealomas,
• obstructive hydrocephalus,
• cysticercosis,
• toxoplasmosis,
• multiple sclerosis,
• arteriovenous malformations.

Any other compression, ischaemia or damage to the midbrain can lead to the syndrome, including: trauma and brainstem-related infections.

Neoplasms and giant aneurysms of the posterior fossa have also been associated with midbrain syndrome.

Vertical supranuclear ophthalmoplegia has also been associated with metabolic disorders, such as Niemann-Pick’s disease, Wilson’s disease, bilirubin encephalopathy (kernittero) and barbiturate overdose.

The main features of Parinaud’s syndrome are:

• upward and – in the case of bilateral lesions – downward gaze paralysis,
• convergence rectus nystagmus;
• lack of convergence;
• dilated pupils (approx. 6 mm) that respond poorly to light, but better to accommodation (dissociation near light).
• Collier’s sign is present and Argyll Robertson’s sign may be present.
• Pupils are mydriatic or normal, with light-accommodation dissociation.
• Bilateral papilledema is often present.

This disorder, especially with regard to gaze paralysis, is difficult to distinguish from progressive supranuclear palsy.

Diagnosis

Diagnosis is based on anamnesis and objective examination.

Confirmation can be made by imaging, such as CT or MRI.

The syndrome is usually diagnosed during an eye or neurological examination.

Treatment for Parinaud’s syndrome

Treatment is mainly directed at the upstream cause of the dorsal midbrain lesion.

A thorough examination, including neuroimaging, is essential to exclude anatomical lesions or other causes of this syndrome.

Visually significant upward paralysis can be alleviated with bilateral recessions of the lower rectus.

Retraction nystagmus and convergence movement are also generally improved with this procedure.

Prognosis

Ocular function in patients with Parinaud’s syndrome generally improves slowly over months, especially with resolution of the upstream causative factor, although this is not always possible as some lesions result in permanent nerve damage; continuous resolution after the first 3-6 months after onset is rare.

Rapid resolution after normalisation of intracranial pressure following placement of a ventriculo-peritoneal shunt has been reported.

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Source:

Medicina Online