chiasmal syndrome

What is Chiasmal Syndrome?

Chiasmal syndrome refers to a set of signs and symptoms associated with lesions or damage to the optic chiasm, which is the anatomical location where the two optic nerves from each eye cross over before separating into the two distinct optic tracts. This condition can manifest as various impairments in the affected individual's visual field, depending on the location and severity of the lesion.

Causes and Types

Chiasmal syndrome can be caused by a variety of factors, including:

• Pituitary adenomas (most common cause)
• Cancer
• Other medical conditions such as multiple sclerosis or craniopharyngioma
• Traumatic head injury

The condition can be categorized into intrinsic (thickening of the chiasm itself) and extrinsic (compression of the chiasm from an adjacent structure) types.

Symptoms

Common symptoms of chiasmal syndrome include:

• Visual field defects, such as bitemporal hemianopia or scotomata
• Loss of central vision
• Difficulty with near tasks
• Binocular visual disturbances

Diagnosis and Imaging

Magnetic resonance imaging (MRI) is the best mode of neuroimaging for most chiasmal lesions and may provide clues to the etiology of an isolated chiasmal syndrome. Other diagnostic tools include visual evoked potentials (VEPs) and neuroimaging studies.

References:

• [1] Chiasmal syndrome is a condition associated with severe head injury, characterized by deficits in pituitary and hypothalamus function due to damage in the optic chiasm. [5]
• [4] Most chiasmal syndromes can be categorized as intrinsic (thickening of the chiasm itself) or extrinsic (compression of the chiasm from an adjacent structure). [11]
• [9] Traumatic chiasmal syndrome, which occurs due to an injury at the level of crossing fibres in the optic chiasma following trauma to the head, is characterised by bitemporal hemianopia or scotomata.

Visual Field Defects

Chiasmal syndrome is characterized by various impairments of the affected's visual field, depending on the location of the lesion along the optic nerve [2]. The most common presenting symptoms include changes in the peripheral visual field [10].

• Bitemporal hemianopia: A loss of vision in the outer half of each eye, resulting from lesions affecting the optic chiasm [1].
• Homonymous hemianopia: A loss of vision on one side of both eyes, caused by lesions affecting the optic tract or lateral geniculate body [2].

Other Symptoms

In addition to visual field defects, chiasmal syndrome may present with a range of other symptoms, including:

• Decreased visual acuity: Reduced sharpness of vision, which can be mild or severe [5].
• Endocrine symptoms: Hormonal imbalances caused by compression of the pituitary gland, leading to symptoms such as:
  • Systemic symptoms secondary to hormonal imbalance (e.g., fatigue, weight gain) [10]
  • Headache and photophobia (sensitivity to light) [9]
• Headache: A common symptom, often accompanied by nausea and vomiting [4].
• Diplopia: Double vision, caused by misalignment of the eyes or compression of the optic nerves [11].

Rare Symptoms

In rare cases, chiasmal syndrome may present with more severe symptoms, including:

• Mental changes: Confusion, altered consciousness, or even coma, resulting from large tumors compressing the optic chiasm and surrounding structures [11].
• Seizures: Rarely, seizures can occur due to compression of the temporal lobe or other brain regions [13].

It is essential to note that these symptoms can vary in severity and presentation depending on the underlying cause and location of the lesion. A thorough medical evaluation, including neuroimaging studies, is necessary for accurate diagnosis and treatment.

References:

[1] Astorga-Carballo et al. (2017) [2] Jefferis et al. (2023) [3] Takahashi et al. (2018) [4] Park et al. [5] The chiasmal syndrome is a constellation of signs and symptoms that include changes in the visual field, decreased visual acuity, endocrine symptoms, headache, diplopia, mental changes, seizures, and other rare symptoms [14]. [6] Clinical neuro-ophthalmic symptoms and corresponding signs of pituitary disease and/or chiasmal compression are summarised in Table 1 [2, 5–9, 14–17].

Treatment Options for Chiasmal Syndrome

Chiasmal syndrome, also known as optic chiasm syndrome, is a condition characterized by visual field defects due to compression or damage to the optic chiasm. While there are various treatment options available, drug treatment plays a crucial role in managing this condition.

• Corticosteroids: Corticosteroids, such as prednisone, are often used to reduce inflammation and swelling around the optic chiasm. This can help alleviate symptoms and improve visual field defects [8].
• Bromocriptine: Bromocriptine is a dopamine agonist that has been used to treat prolactinomas, which can cause chiasmal syndrome. It works by reducing prolactin levels and alleviating compression on the optic chiasm [5].
• Corticosteroids with bromocriptine: In some cases, corticosteroids may be combined with bromocriptine to enhance treatment efficacy. This combination has been shown to improve visual outcomes in patients with chiasmal syndrome [8].

Other Treatment Modalities

While drug treatment is essential, other modalities like surgery and radiation therapy are also used to manage chiasmal syndrome.

• Surgery: Surgical decompression may be necessary to relieve compression on the optic chiasm. This can involve resection of a tumor or other lesion causing the compression [14].
• Radiation therapy: Radiation therapy is another option for treating chiasmal syndrome, particularly in cases where surgery is not feasible or has failed [6].

Key Points

• Corticosteroids and bromocriptine are commonly used drug treatments for chiasmal syndrome.
• Combination therapy with corticosteroids and bromocriptine may enhance treatment efficacy.
• Surgery and radiation therapy are also used to manage chiasmal syndrome, particularly in cases where compression is severe.

References:

[5] by A Moumen · 2021 [6] by D Al-Bader · 2022 · Cited by 5 [8] Aug 27, 2021 [14] Introduction. Patients with pituitary macroadenomas typically present with bitemporal hemianopsia...

Differential Diagnosis of Chiasmal Syndrome

Chiasmal syndrome, also known as traumatic chiasmal syndrome, is a condition associated with severe head injury, characterized by deficits in pituitary and hypothalamus function due to damage in the optic chiasm. The differential diagnosis of chiasmal syndrome includes various conditions that can mimic its symptoms.

Common Causes:

• Pituitary Adenomas: These are the most common cause of chiasmal syndrome, accounting for approximately 50% of cases.
• Cavernous Sinus Meningiomas: These tumors can compress the optic chiasm and lead to similar symptoms.
• Aneurysms: Ruptured aneurysms in the circle of Willis can cause damage to the optic chiasm and result in chiasmal syndrome.
• Schwannomas: These benign tumors can grow on the nerves and compress the optic chiasm, leading to chiasmal syndrome.

Other Conditions:

• Multiple Sclerosis: This autoimmune disease can cause demyelination of the optic nerve and lead to visual symptoms similar to those seen in chiasmal syndrome.
• Neurosarcoidosis: This condition involves inflammation of the nervous system and can cause damage to the optic chiasm, leading to chiasmal syndrome.
• Traumatic Brain Injury: Severe head injury can cause damage to the optic chiasm and result in chiasmal syndrome.

Symptoms:

The symptoms of chiasmal syndrome include:

• Visual Loss: Bitemporal hemianopsia is a classic presentation, where there is loss of both temporal fields.
• Field Defects: Patients may experience problems with central vision, difficulty with near tasks, and binocular visual disturbances.
• Pituitary Dysfunction: Hormonal imbalances can occur due to damage to the pituitary gland.

References:

[1] Chiasmal Syndrome is defined as a condition associated with severe head injury, characterized by deficits in pituitary and hypothalamus function due to damage in the optic chiasm. (Source: [2])

[3] Pituitary adenomas are the most common cause of chiasmal syndrome, accounting for approximately 50% of cases. (Source: [11])

[4] Cavernous sinus meningiomas can compress the optic chiasm and lead to similar symptoms. (Source: [9])

[5] Neurosarcoidosis involving the chiasmal region should be considered in the differential diagnosis of chiasmal infection, especially in African-American patients. (Source: [14])