Utility of transcranial doppler in idiopathic intracranial hypertension

Evaluation of cerebrovascular hemodynamics in patients with idiopathic intracranial hypertension using transcranial Doppler

Background

Idiopathic intracranial hypertension (IIH) is a disorder of increased intracranial pressure without a clear cause and can have serious visual effects. Previous research work suggests that transcranial Doppler measurements of pulsatility index correlate accurately with elevated intracranial pressure.

Objective

To assess the cerebrovascular hemodynamic changes in patients with IIH using transcranial Doppler before and after lumbar puncture and CSF withdrawal.

Methods

An interventional study conducted on 40 patients (31 females and 9 males) fulfilling the modified Dandy criteria for diagnosis of idiopathic intracranial hypertension, MRI brain, and MRV was done to the patients. Lumbar puncture was done for all included patients to measure intracranial pressure and CSF withdrawal. Transcranial Doppler was performed for all included before and after lumbar puncture and CSF withdrawal and the following parameters were measured: peak systolic velocity (PSV), end diastolic velocity (EDV), resistivity index (RI), and pulsatility index (PI).

Results

Significant relation was found between grades of papilledema and PSV, RI, and PI (p value 0.012, 0.025, 0.016) but no significant relation was found between grades of papilledema and EDV (0.102). Significant changes occurred in parameters of TCD pre- and post-CSF withdrawal including PSV, EDV, and PI (p value 0.001, 0.015, 0.019) denoting a significant change in cerebral hemodynamics after CSF withdrawal which denotes a decrease in intracranial pressure.

Conclusion

Increased intracranial pressure significantly affects cerebral blood flow. A normalization of transcranial Doppler parameters occurs following lowering of intracranial pressure through lumbar puncture and CSF withdrawal.

Transcranial Doppler for Monitoring and Evaluation of Idiopathic Intracranial Hypertension

Background  Idiopathic intracranial hypertension (IIH) is a disorder of unknown origin, characterized by features of raised intracranial pressure (ICP). Existing literature is inconclusive about the role of transcranial Doppler (TCD) in the management of IIH. Objective  To study the TCD changes in IIH patients, pre- and post-cerebrospinal fluid (CSF) drainage. Materials and Methods  This was a prospective study, conducted between July 2017 and December 2019, in a tertiary care referral center in South India. Sixteen consecutive patients, suspected to have IIH, underwent magnetic resonance imaging ofthe brain, a baseline TCD, and lumbar puncture with CSF drainage and pressure monitoring. Post-CSF drainage, TCD was repeated and mean flow velocities, peak systolic velocities, end-diastolic velocities, and pulsatility index (PI), in the middle cerebral artery (MCA), vertebral artery, and basilar artery (BA) were noted. Thirteen patients had elevated CSF pressure, and fulfilled the diagnostic criteria for IIH. These patients were included in the final analysis and pre- and post-CSF drainage TCD blood flow velocities and PI were compared. Results  The mean age of study participants was 29.92 ± 6.92 years. There was a significant reduction in the cerebral flow velocities in bilateral MCA, after CSF drainage and normalization of ICP. Flow velocities in posterior circulation and PI in MCA, PCA, and BA showed an insignificant reduction. Two patients, who did not show any reduction in flow velocities after CSF drainage, developed optic atrophy on follow-up. Conclusion  TCD-derived systolic blood flow velocities can be used in the management and follow-up of patients with IIH.

Noninvasive methods of detecting increased intracranial pressure

The detection of elevated intracranial pressure (ICP) is of paramount importance in the diagnosis and management of a number of neurologic pathologies. The current gold standard is the use of intraventricular or intraparenchymal catheters; however, this is invasive, expensive, and requires anesthesia. On the other hand, diagnosing intracranial hypertension based on clinical symptoms such as headaches, vomiting, and visual changes lacks sensitivity. As such, there exists a need for a noninvasive yet accurate and reliable method for detecting elevated ICP. In this review, we aim to cover both structural modalities such as computed tomography (CT), magnetic resonance imaging (MRI), ocular ultrasound, fundoscopy, and optical coherence tomography (OCT) as well as functional modalities such as transcranial Doppler ultrasound (TCD), visual evoked potentials (VEPs), and near-infrared spectroscopy (NIRS).

Noninvasive intracranial hypertension detection utilizing semisupervised learning

Intracranial pressure (ICP) monitoring is an established clinical practice in managing patients with risk of acute ICP elevation although the clinically accepted way of measuring ICP remains invasive. However, the invasive nature of ICP measurement obviates its application in many clinical circumstances such as diagnosis of idiopathic intracranial hypertension (IH). We propose a noninvasive diagnostic tool for IH based on the morphological analysis of cerebral blood flow velocity waveforms. We mainly compare two types of IH detection methods: one based on the traditional supervised learning approach and the other based on the semisupervised learning approach. Our simulation results demonstrate that the predictive accuracy (area under the curve) of the semisupervised IH detection method can be as high as 92% while that of the supervised IH detection method is only around 82%. It should be noted that the predictive accuracy of the pulsatility index (PI)-based IH detection method is as low as 59%. Although the predictive accuracy is a widely used accuracy measurement, it does not consider clinical consequences of necessary and unnecessary treatments. For this reason, we have adopted the decision curve analysis to address this issue. The decision curve analysis results show that the semisupervised IH detection method is not only more accurate, but also clinically more useful than the supervised IH detection method or the PI-based IH detection method.

[Specific treatment for intracerebral hemorrhage. Experts' recommendations: stroke management in the intensive care unit]

Spontaneous intracerebral hemorrhages represent from 10 to 15% of strokes. They can be defined by the eruption of arterial blood within the cerebral parenchyma. Clinical signs are not specific and the diagnosis can only be made using brain imaging techniques (CT or magnetic resonance imaging). Management of intracerebral hemorrhage combines general measures (neurovascular intensive care unit, treatment of high blood pressure and of neurotoxic factors) with more specific measures including correction of coagulation abnormalities and, in some cases, neurosurgical treatment.

Inter-subject correlation exists between morphological metrics of cerebral blood flow velocity and intracranial pressure pulses

BACKGROUND

The prototypical intracranial pressure (ICP) pulse morphology has been well known to be triphasic. Several studies suggest that the morphology of ICP pulse reflects the physiological and pathophysiological conditions of the intracranial dynamics. Recently, there has been a renaissance of studying ICP pulse using new ICP signal processing technologies in various clinical contexts. Cerebral blood flow velocity (CBFV) pulse is another important pulsatile signal originated from the complex circulatory systems of cerebral blood flow. However, CBFV pulse morphology has not been well studied mainly due to the noise level and lack of signal processing techniques.

METHODS

Our group recently developed a technique called the morphological clustering and analysis of intracranial pressure that can extract a comprehensive set of pulse morphological metrics. We extend this algorithm to extract various morphological metrics from ICP and CBFV pulses that were simultaneously recorded from 47 brain injury patients and investigate the mutual correlation between those metrics utilizing the robust percentage bend correlation analysis.

RESULTS

Our results show that CBFV pulses are also triphasic as ICP pulses and 15.2% of 128 pulse morphological metrics extracted from ICP and CBFV pulses are highly correlated (P < 0.01) in an inter-subject fashion. In addition, mean ICP does not correlate (P = 0.45) with the pulsatility index of CBFV pulses but correlates (P < 0.05) with several novel CBFV pulse morphological metrics such as the time interval between the onset of CBFV pulses and ECG QRS peak.

CONCLUSIONS

Our results suggest that characterizing CBFV pulse morphology is clinically important because it may offer a potential noninvasive alternative to assess various aspects of ICP such as mean ICP.