Parinaud's syndrome

Overview

Parinaud’s syndrome, also known as dorsal midbrain syndrome or pretectal syndrome, is a rare neurological disorder that results from damage to the dorsal midbrain. It primarily affects vertical eye movement, pupillary reactions, and eyelid function. The condition is named after Henri Parinaud, a French neurologist who first described the constellation of eye movement abnormalities associated with lesions in the upper midbrain. Parinaud’s syndrome is most commonly associated with tumors, vascular lesions, or inflammatory processes in the midbrain area. Early recognition is crucial, as the syndrome may indicate a serious underlying condition such as a pineal tumor or stroke.

Causes

Parinaud’s syndrome arises due to disruption of the vertical gaze centers and nearby structures in the dorsal aspect of the midbrain, particularly in the region of the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), the posterior commissure, and the superior colliculi. Common causes include:

• Pineal gland tumors: Such as germinomas or pineocytomas, which compress the dorsal midbrain.

• Hydrocephalus: Enlargement of the third ventricle can cause pressure on the dorsal midbrain.

• Multiple sclerosis (MS): Inflammatory demyelination affecting the midbrain.

• Midbrain strokes or infarcts: Ischemia in the posterior circulation supplying the midbrain.

• Arteriovenous malformations (AVMs): Vascular malformations in or near the midbrain.

• Trauma: Head injuries leading to localized damage in the dorsal midbrain.

• Infections or inflammatory diseases: Including tuberculosis or sarcoidosis involving the brainstem.

Symptoms

Parinaud’s syndrome presents with a distinctive set of ocular and neurological signs, which may be accompanied by symptoms of the underlying cause. Key features include:

Ocular Motor Abnormalities

• Vertical gaze palsy: Impaired ability to move the eyes up or down, especially upward gaze.

• Convergence-retraction nystagmus: Jerky, inward movement of the eyes when attempting to look upward.

• Light-near dissociation: Pupils that constrict during near vision tasks (accommodation) but do not react to light.

• Eyelid retraction (Collier’s sign): An abnormally wide palpebral fissure, giving a "staring" appearance.

• Pseudo-Argyll Robertson pupils: Pupils that react poorly to light but constrict on near effort.

Other Associated Symptoms

• Diplopia: Double vision due to impaired ocular coordination.

• Blurred vision or difficulty reading: Due to gaze and convergence abnormalities.

• Headaches, nausea, or vomiting: Especially in cases related to tumors or hydrocephalus.

• Ataxia or imbalance: If associated with involvement of adjacent cerebellar pathways.

Diagnosis

Diagnosis of Parinaud’s syndrome is clinical, based on the characteristic ocular signs and supported by neuroimaging and other investigations to identify the underlying cause. The diagnostic workup typically includes:

• Neurological and ophthalmological examination: To assess eye movements, pupil responses, and associated neurologic signs.

• MRI of the brain: Preferred imaging modality to detect midbrain lesions, pineal region tumors, or demyelinating plaques.

• CT scan: Useful in emergency settings or when hydrocephalus is suspected.

• Lumbar puncture: May be indicated if infection, inflammation, or malignancy is suspected.

• Blood tests: To evaluate for autoimmune or infectious causes, including tuberculosis, sarcoidosis, or MS.

• Visual field testing: To assess the functional impact of the ocular deficits.

Treatment

Treatment of Parinaud’s syndrome focuses on addressing the underlying cause of the dorsal midbrain lesion. Symptomatic management of eye movement abnormalities is also part of supportive care.

1. Treatment of the Underlying Cause

• Tumors: Surgical resection, chemotherapy, or radiation therapy may be required for pineal region tumors.

• Hydrocephalus: May necessitate ventricular shunting or endoscopic third ventriculostomy to relieve pressure.

• Multiple sclerosis: Managed with corticosteroids and disease-modifying therapies.

• Stroke: Supportive care and rehabilitation; antiplatelet or anticoagulant therapy may be used depending on the cause.

• Infections or inflammation: Appropriate antimicrobial or immunosuppressive therapy, such as antitubercular treatment or corticosteroids for sarcoidosis.

2. Symptomatic and Supportive Care

• Prism glasses or visual aids: May help alleviate diplopia.

• Occupational therapy: To assist with vision-related functional tasks.

• Eye movement exercises: Sometimes prescribed to improve voluntary control and adaptation.

Prognosis

The prognosis of Parinaud’s syndrome largely depends on the underlying cause and the extent of midbrain damage. In some cases, particularly when due to reversible causes such as hydrocephalus or inflammation, significant recovery is possible with timely treatment. In other cases, especially with irreversible lesions like tumors or infarcts, eye movement abnormalities may persist long-term.

Persistent deficits in vertical gaze or pupil reactivity may impact daily activities, but supportive therapies can help patients adapt. Early detection and appropriate treatment of the underlying condition significantly improve outcomes and reduce the risk of complications.