Sonographic evaluation of optic nerve sheath diameter in idiopathic intracranial hypertension

Is Lumbar Puncture Needed? - Noninvasive Assessment of ICP Facilitates Decision Making in Patients with Suspected Idiopathic Intracranial Hypertension

PURPOSE

 Idiopathic intracranial hypertension (IIH) usually occurs in obese women of childbearing age. Typical symptoms are headache and sight impairment. Lumbar puncture (LP) is routinely used for both diagnosis and therapy (via cerebrospinal fluid drainage) of IIH. In this study, noninvasively assessed intracranial pressure (nICP) was compared to LP pressure (LPP) in order to clarify its feasibility for the diagnosis of IIH.

MATERIALS AND METHODS

 nICP was calculated using continuous signals of arterial blood pressure and cerebral blood flow velocity in the middle cerebral artery, a method which has been introduced recently. In 26 patients (f = 24, m = 2; age: 33 ± 11 years), nICP was assessed one hour prior to LPP. If LPP was > 20 cmH₂O, lumbar drainage was performed, LPP was measured again, and also nICP was reassessed.

RESULTS

 In total, LPP and nICP correlated with R = 0.85 (p < 0.001; N = 38). The mean difference of nICP-LPP was 0.45 ± 4.93 cmH₂O. The capability of nICP to diagnose increased LPP (LPP > 20 cmH₂O) was assessed by ROC analysis. The optimal cutoff for nICP was close to 20 cmH₂O with both a sensitivity and specificity of 0.92. Presuming 20 cmH₂O as a critical threshold for the indication of lumbar drainage, the clinical implications would coincide in both methods in 35 of 38 cases.

CONCLUSION

 The TCD-based nICP assessment seems to be suitable for a pre-diagnosis of increased LPP and might eliminated the need for painful lumbar puncture if low nICP is detected.

Noninvasive methods to monitor intracranial pressure

PURPOSE OF REVIEW

Intracranial pressure (ICP) is determined by the production of and outflow facility of cerebrospinal fluid. Since alterations in ICP are implicated in several vision-threatening and life-threatening diseases, measurement of ICP is necessary and common. All current clinical methods to measure ICP are invasive and carry the risk for significant side effects. Therefore, the development of accurate, reliable, objective, and portal noninvasive devices to measure ICP has the potential to change the practice of medicine. This review discusses recent advances and barriers to the clinical implementation of noninvasive devices to determine ICP.

RECENT FINDINGS

Many noninvasive methods to determine ICP have been developed. Although most have significant limitations limiting their clinical utility, several noninvasive methods have shown strong correlations with invasively obtained ICP and have excellent potential to be developed further to accurately quantify ICP and ICP changes.

SUMMARY

Although invasive methods remain the mainstay for ICP determination and monitoring, several noninvasive biomarkers have shown promise to quantitatively assess and monitor ICP. With further refinement and advancement of these techniques, it is highly possible that noninvasive methods will become more commonplace and may complement or even supplant invasively obtained methods to determine ICP in certain situations.

Non-invasive detection of intracranial pressure related to the optic nerve

Intracranial pressure (ICP) is associated with a variety of diseases. Early diagnosis and the timely intervention of elevated ICP are effective means to clinically reduce the morbidity and mortality of some diseases. The detection and judgment of reduced ICP are beneficial to glaucoma doctor and neuro ophthalmologist to diagnose optic nerve disease earlier. It is important to evaluate and monitor ICP clinically. Although invasive ICP detection is the gold standard, it can have complications. Most non-invasive ICP tests are related to the optic nerve and surrounding tissues due to their anatomical characteristics. Ultrasound, magnetic resonance imaging, transcranial Doppler, papilledema on optical coherence tomography, visual evoked potential, ophthalmodynamometry, the assessment of spontaneous retinal venous pulsations, and eye-tracking have potential for application. Although none of these methods can completely replace invasive technology; however, its repeatable, low risk, high accuracy, gradually attracted people's attention. This review summarizes the non-invasive ICP detection methods related to the optic nerve and the role of the diagnosis and prognosis of neurological disorders and glaucoma. We discuss the advantages and challenges and predict possible areas of development in the future.

Combined accuracy of optic nerve sheath diameter, strain ratio, and shear wave elastography of the optic nerve in patients with idiopathic intracranial hypertension

PURPOSE

This study assessed the combined accuracy of optic nerve sheath diameter (ONSD), strain ratio (SR), and shear wave elastography (SWE) of the optic nerve (ON) in patients with idiopathic intracranial hypertension (IIH).

METHODS

This prospective study was carried out on both ONs of 34 consecutive patients diagnosed with IIH and 16 age- and sex-matched healthy volunteers. All of the study participants were women. The ONSD, SR, and SWE of the ON were measured. The severity of papilledema of IIH patients was sub-classified into mild papilledema and moderate/severe papilledema.

RESULTS

The mean ONSD (5.6±1.1 mm), SR (0.7±0.1), and SWE (30.1±16.7 kPa) of the IIH patients were significantly different (P=0.001) from the ONSD (4.1±0.5 mm), SR (0.9±0.1), and SWE (8.2±3.4 kPa) of controls. The cutoff values of ONSD, SR, and SWE of the ON for differentiating IIH patients from controls were 5.45 mm, 0.8, and 10.3 kPa with areas under the curve (AUCs) of 0.91, 0.86, and 0.96 and accuracy values of 91%, 81%, and 93%, respectively. Combined SWE and ONSD and combined SWE, ONSD, and SR for differentiating IIH patients from controls revealed AUCs of 0.98 and 0.99 and accuracy values of 96% and 96%, respectively. ONSD, SR, and SWE showed significant differences between mild and moderate/severe papilledema (P=0.001). Papilledema was correlated with SWE (r=0.8, P=0.001), ONSD (r=0.4, P=0.001), and SR (r=-0.4, P=0.001).

CONCLUSION

The combination of ONSD, SR, and SWE may be helpful for diagnosing IIH, and a good indicator of the degree of papilledema.