Compressive Optic Neuropathy Workup
- Author: Jonathan W Kim, MD; Chief Editor: Hampton Roy, Sr, MD more...
Blood tests are sometimes helpful in the diagnosis of compressive optic neuropathy. However, the serologic workup should be guided by the history and clinical presentation.
If thyroid ophthalmopathy is suspected, blood tests for thyroid function and anti-thyroid antibodies should be performed.
An elevated angiotensin-converting enzyme level may be seen in 52%-90% of patients with active sarcoidosis.
An elevated prostate specific antigen (PSA) level may be helpful in male patients with suspected bony orbital metastases and optic nerve compression.
Insulin-like growth factor 1 (IGF-1), prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyrotropin-releasing hormone (TRH) and alpha subunit, cortisol, and thyroxine (T4) can be obtained to assess a pituitary tumor.
Alkaline phosphatase levels would be elevated in Paget disease of bone; an elevated bone-specific alkaline phosphatase (BSAP) has 84% sensitivity.
Whenever there is clinical suspicion of compressive optic neuropathy (CON), a neuroimaging study is mandatory to determine the presence and location of the responsible lesion. With the sensitivity and specificity of modern neuroimaging, a negative scan essentially rules out the possibility of CON as the cause of vision loss.
In most cases of CON, magnetic resonance imaging (MRI) is the imaging modality of choice because of the excellent soft-tissue resolution of the anterior visual pathway and parasellar area; typically an orbit and brain MRI with and without contrast is ordered to evaluate a patient for CON.Abnormalities within the peri-optical spaces are more consistent with meningiomas, whereas a global increase in the size of the optic nerve is in favor of a glioma. Example MRIs are shown below.
Computed tomography (CT) scanning offers excellent visualization of the bony anatomy and is particularly useful to evaluate the intraconal space of the orbit. However, for imaging the orbital apex and optic canal, MRI is preferred over CT due to the absence of signal interference from adjacent bone seen on tomography.
Ultrasonography may be useful to document the presence of anterior orbital lesions but offers limited penetration into the deep orbit. However, in certain clinical situations, ultrasonography may be used to image patients quickly in the office in order to determine whether CT or MRI is warranted.
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