What is Parinaud Syndrome?
In the late 1800s, a French eye doctor named Henri Parinaud first identified a condition that now goes by the name Parinaud syndrome. He found this in a group of patients who had difficulty with coordinated eye movements and paralysis of the gaze. Parinaud believed that the root cause of this condition was damage to a specific section of the brain known as the quadrigeminal area.
This condition is known by different names such as the Sylvian aqueduct syndrome, dorsal midbrain syndrome, Pretectal syndrome, and Koerber-Salus-Elschnig syndrome. Initially, Parinaud characterized this condition by upward gaze palsy and an inability to move the eyes towards the nose, a condition known as convergence paralysis.
However, the understanding of Parinaud syndrome has since evolved to include three main features: paralysis when trying to look upwards, shakiness of the eyes when trying to bring the eyes in toward the nose (convergence retraction nystagmus), and irregular responses of the pupils to light and proximity (pupillary light-near dissociation). In some cases, it could also include a downward gaze in a normal eye position, and in rare instances, an inability to move the gaze downward (downgaze palsy).
What Causes Parinaud Syndrome?
Parinaud syndrome can be caused by a variety of factors. Some of these include tumors in the pineal gland (a small gland in the brain), damage to the middle part of the brain due to a stroke (known as midbrain infarctions), the disease multiple sclerosis, bleeding into the midbrain (midbrain hemorrhage), brain inflammation (encephalitis), abnormal connections between arteries and veins, infections like toxoplasmosis, and trauma or injury to the brain. One other possible cause can be obstructive hydrocephalus, which is when there’s excessive fluid in the brain, and in rare cases, a type of seizure known as tonic-clonic.
There have also been instances of Parinaud syndrome occurring after a procedure called brachytherapy, which is a form of radiation treatment. However, the most frequent causes tend to be a tumor in the pineal gland or issues related to the midbrain like stroke and bleeding.
It’s interesting to note that what causes Parinaud syndrome can differ based on age. Tumors (neoplastic causes) are more commonly found in children and young adults, while issues with the blood vessels (vascular causes) are often seen in middle-aged individuals and seniors.
Risk Factors and Frequency for Parinaud Syndrome
Parinaud’s syndrome is typically a standalone condition. Common causes could be tumors in the pineal gland or damages to the mid-section of the brain. Roughly, 65% of cases are caused by primary lesions in the midbrain, such as stroke, bleeding, or cancer. Almost a third of the cases can be attributed to tumors in the pineal gland which put pressure on the reflex centers in the dorsal midbrain.
The standard set of symptoms, including difficulties in gazing upwards, abnormal eye movements, and the pupil’s abnormal response to light and proximity (known as light-near dissociation), can be observed in about 65% of individuals with Parinaud’s syndrome.
- Parinaud’s syndrome usually presents as an isolated condition.
- The most common causes include tumors in the pineal gland or damages to the middle section of the brain.
- About 65% of cases are a result of primary lesions in the midbrain, such as stroke, bleeding, or cancer.
- Close to 30% of cases are due to pineal gland tumors which cause pressure on the reflex centers in the dorsal midbrain.
- About 65% of people with Parinaud’s syndrome exhibit a trio of symptoms: difficulties in upward gazing, abnormal eye movements, and abnormal pupil’s response to light and proximity.
Signs and Symptoms of Parinaud Syndrome
Parinaud syndrome is a condition known for three main symptoms: trouble with upward eye movement, twitchy eye movement when trying to focus close up (also called “convergence retraction nystagmus”), and a diminished response of the pupils to light. People with this syndrome often report difficulties in looking upwards, watery and distorted near vision, seeing double, and they may also have related neurological symptoms. Double vision is the most common symptom, affecting 65% of individuals. It can either be due to a slight misalignment of the eyes or a condition affecting the fourth cranial nerve. Vertical double vision is particularly common and can greatly disrupt the patient’s quality of life. Some folks may also report blurred sight, possibly due to a spasm in the eye’s focusing system. The most debilitating symptom for many is the inability to move the eyes upwards, frequently forcing them to compensate by raising their chin.
Parinaud syndrome presents several other signs to look for:
- An inability to move the eyes vertically, particularly difficulties with looking upwards. Sometimes, this comes along with issues in downward gaze, but there are rare instances where only downward gaze is affected. The reflex controlling eye movements during head movement is usually not impacted
- Convergence retraction nystagmus, a symptom where the eyes twitch when attempting to look upwards
- Diminished pupil response to light
- Loss of convergence, a symptom seen in less than a quarter of patients
- Upper eyelid retraction also called the ‘tucked lid’ sign, a symptom seen in about 40% of patients
- A downward eye position also known as the ‘setting sun’ sign’
Testing for Parinaud Syndrome
It’s important that all patients receive a thorough check of their neurological system. This includes checking vision sharpness, field of view, color recognition, pupil response, and examination of the back of the eye (or ‘fundoscopy’). Through this, a variety of health conditions can be detected.
Given the numerous potential causes of these health conditions, it’s essential to perform a thorough investigation that could include neuroimaging, a technique that allows doctors to see an image of your brain. It’s crucial to identify what might be causing these issues.
The doctors may also conduct infection screening, tests to measure the proteins in your blood and check how well your thyroid is functioning. Additional tests could be cerebrospinal fluid studies (to assess the fluid surrounding your brain and spinal cord), and checking the presence of acetylcholine receptor antibodies in the blood (which can indicate certain diseases). Also, nerve conduction studies might be considered to evaluate how your nerves are functioning.
Treatment Options for Parinaud Syndrome
The primary goal of treatment is to address the root cause of the problem. If hydrocephalus, a condition where fluid builds up in the brain, is caught early enough, its symptoms may be completely reversed. Therefore, it’s important to treat the underlying condition promptly before permanent damage is caused.
If someone constantly gazes upward due to an issue with their eye muscles, surgical procedures are available to help correct it. These procedures may involve weakening the lower eye muscle (inferior rectus recession), strengthening the upper eye muscle (superior rectus resection), or changing the position of the eye muscles responsible for movement to the left or right (transposition of medial and lateral rectus muscles). All these operations aim to improve gaze position, reduce unusual head movements, and decrease the severity of rapid, uncontrolled eye movements known as retraction nystagmus.
Besides surgery, visual training and exercises designed to improve eye tracking can be utilized, which could be particularly helpful for those with chronic gaze palsies, a condition where movement of the eyes is limited or difficult.
What else can Parinaud Syndrome be?
If you are experiencing certain neurological symptoms, your doctor might check for medical conditions that can cause them. Here are some possibilities:
- Arteriovenous malformation (AV malformation)
- Compression by a mass in the pineal region of the brain
- Dilation of the third ventricle in the brain
- Lesions in the posterior commissure and Midbrain Reticular Formation (MRF)
- Infarction, or blockage in the blood supply, in the midbrain
- Multiple sclerosis, a disease affecting the brain and spinal cord
