Applications for ICP measurement in neurology and neurosurgery include the management of trauma, stroke, malignancy, hydrocephalus, shunt malfunction, craniofacial abnormalities, pseudotumor cerebri, migraine and other causes of chronic headache, and infection. Indications for non-invasive ICP measurement are the same, although non-invasive measurement should not be used when external CSF drainage might assist in the management of increased ICP.
Another application for ICP measurement is the diagnosis and management of glaucoma. Glaucoma is the second leading cause of blindness globally.*
Raised IOP is a risk factor for developing glaucoma, which is usually defined in terms of high IOP. Nevertheless, there is no definite threshold for intraocular pressure that causes glaucoma. One person may develop nerve damage at a relatively low-pressure, while another person may have high IOP for years and never develop nerve damage.** Uncontrolled glaucoma progression leads to permanent damage of the optic nerve and visual field loss. These can result in blindness, which is why Glaucoma has been nicknamed “sneak thief of sight.” Damage may only be recognized at later stages of the disease. The same neuropathy can occur, however, even in the absence of elevated IOP. This syndrome has been called Normal Tension Glaucoma (NTG) or Low Tension Glaucoma (LTG).
NTG and LTG have the characteristics and visual-field loss of high tension glaucoma but show consistently normal IOP ( < 22 mm Hg). The number of patients with LTG and NTG may be equal to that of patients with high IOP. It is thought that as many patients may have LTG and NTG as have high tension glaucoma
Studies undertaken using Vittamed’s non-invasive intracranial pressure measurement instrument indicate that the normal gradient between IOP and ICP is reversed in NTG and LTG. Indeed, diagnosis depends on the ability to compare IOP and ICP.***
It is impractical to measure and follow ICP routinely using current, invasive ICP monitoring methods. The development of self-calibrating non-invasive ICP is offers a new and effective approach to the diagnosis and management of patients with LTG and NTG.
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