N. Keong

Clinical assessment of cerebrospinal fluid dynamics in hydrocephalus. Guide to interpretation based on observational study.

Weerakkody RA, Czosnyka M, Schuhmann MU, Schmidt E, Keong N, Santarius T, Pickard JD, Czosnyka Z. Clinical assessment of cerebrospinal fluid dynamics in hydrocephalus. Guide to interpretation based on observational study. 
Acta Neurol Scand: 2011: 124: 85–98.
© 2011 John Wiley & Sons A/S.

Index of cerebrospinal compensatory reserve in hydrocephalus.

OBJECTIVEAn index of cerebrospinal compensatory reserve (RAP) has been introduced as a potential descriptor of neurological deterioration after head trauma. It is numerically computed as a linear correlation coefficient between the mean intracranial pressure and the pulse amplitude of the pressure waveform. We explore how RAP varies with different forms of physiological or nonphysiological intracranial volume loads in adult hydrocephalus, with and without a functioning cerebrospinal fluid (CSF) shunt. METHODSA database of intracranial pressure recordings during CSF infusion studies and overnight monitoring in hydrocephalic patients was reviewed for clinical comparison of homogeneous subgroups of patients with hypothetical differences of pressure-volume compensatory reserve. The database includes 980 patients of mixed etiology: idiopathic normal pressure hydrocephalus (NPH), 47%; postsubarachnoid hemorrhage NPH, 12%; noncommunicating hydrocephalus, 22%; others, 19%. All CSF compensatory parameters were calculated by using intracranial pressure waveforms. RESULTSIn NPH, RAP correlated strongly with the resistance to CSF outflow (rs = 0.35; P = 0.045), but weakly correlated with ventriculomegaly (rs = 0.13; P = 0.41). In idiopathic nonshunted NPH patients, RAP did not correlate significantly with elasticity calculated from the CSF infusion test (rs = 0.11; P = 0.21). During infusion studies, RAP increased in comparison to values recorded at baseline (from a median of 0.45–0.86, P = 0.14 * 10−8), indicating a narrowing of the volume-pressure compensatory reserve. During B-waves associated with the REM (rapid eye movement) phase of sleep, RAP increased from a median of 0.53 to 0.89; P = 1.2 * 10−5. After shunting, RAP decreased (median before shunting, 0.59; median after shunting, 0.34; P = 0.0001). RAP also showed the ability to reflect the functional state of the shunt (patent shunt median, 0.36; blocked shunt median, 0.84; P = 0.0002). CONCLUSIONRAP appears to characterize pressure-volume compensatory reserve in patients with hydrocephalus.

Ventriculostomy for control of raised ICP in acute traumatic brain injury

UNLABELLED The aim of this study was to evaluate the effect of ventriculostomy on intracranial pressure (ICP), and related parameters, including cerebrospinal compensation, cerebral oxygenation (PbtO2) and metabolism (microdialysis) in patients with traumatic brain injury (TBI). MATERIALS AND METHODS Twenty-four patients with parenchymal ICP sensors were prospectively included in the study. Ventriculostomy was performed after failure to control ICP with initial measures. Monitoring parameters were digitally recorded before and after ventriculostomy and compared using appropriate tests. RESULTS In all patients ventriculostomy led to rapid reduction in ICP. Pooled mean daily values of ICP remained < 20mmHg for 72h after ventriculostomy and were lower than before (p < 0.001). In 11 out of 24 patients during the initial 24-h period following ventriculostomy an increase in ICP to values exceeding 20mmHg was observed. In the remaining 13 patients ICP remained stable, allowing reduction in the intensity of treatment. In this group ventriculostomy led to significant improvement in craniospinal compensation (RAP index), cerebral perfusion pressure and PbtO2. Improvement in lactate/pyruvate ratio, a marker of energy metabolism, was correlated with the increase in PbtO2. CONCLUSION Ventriculostomy is a useful ICP-lowering manoeuvre, with sustained ICP reduction and related physiological improvements achieved in > 50% of patients.

How does CSF dynamics change after shunting

Objective –  Hydrocephalus is much more complex than a simple disorder of cerebrospinal fluid (CSF) circulation. Shunting primarily corrects disturbed fluid flow which may have an impact on cerebral blood flow and metabolism. We studied hydrocephalic patients before and after shunting to characterize changes in their CSF compensatory parameters.

Imaging normal pressure hydrocephalus: theories, techniques, and challenges

The pathophysiology of NPH continues to provoke debate. Although guidelines and best-practice recommendations are well established, there remains a lack of consensus about the role of individual imaging modalities in characterizing specific features of the condition and predicting the success of CSF shunting. Variability of clinical presentation and imperfect responsiveness to shunting are obstacles to the application of novel imaging techniques. Few studies have sought to interpret imaging findings in the context of theories of NPH pathogenesis. In this paper, the authors discuss the major streams of thought for the evolution of NPH and the relevance of key imaging studies contributing to the understanding of the pathophysiology of this complex condition.

Impact of duration of symptoms on CSF dynamics in idiopathic normal pressure hydrocephalus

Czosnyka Z, Owler B, Keong N, Santarius T, Baledent O, Pickard JD, Czosnyka M. Impact of duration of symptoms on CSF dynamics in idiopathic normal pressure hydrocephalus.
Acta Neurol Scand: 2011: 123: 414–418.
© 2010 John Wiley & Sons A/S.

Pulse amplitude of intracranial pressure waveform in hydrocephalus

BACKGROUND There is increasing interest in evaluation of the pulse amplitude of intracranial pressure (AMP) in explaining dynamic aspects of hydrocephalus. We reviewed a large number of ICP recordings in a group of hydrocephalic patients to assess utility of AMP. MATERIALS AND METHODS From a database including approximately 2,100 cases of infusion studies (either lumbar or intraventricular) and overnight ICP monitoring in patients suffering from hydrocephalus of various types (both communicating and non-communicating), etiology and stage of management (non-shunted or shunted) pressure recordings were evaluated. For subgroup analysis we selected 60 patients with idiopathic NPH with full follow-up after shunting. In 29 patients we compared pulse amplitude during an infusion study performed before and after shunting with a properly functioning shunt. Amplitude was calculated from ICP waveforms using spectral analysis methodology. FINDINGS A large amplitude was associated with good outcome after shunting (positive predictive value of clinical improvement for AMP above 2.5 mmHg was 95%). However, low amplitude did not predict poor outcome (for AMP below 2.5 mmHg 52% of patients improved). Correlations of AMP with ICP and Rcsf were positive and statistically significant (N = 131 with idiopathic NPH; R = 0.21 for correlation with mean ICP and 0.22 with Rcsf; p< 0.01). Correlation with the brain elastance coefficient (or PVI) was not significant. There was also no significant correlation between pulse amplitude and width of the ventricles. The pulse amplitude decreased (p < 0.005) after shunting. CONCLUSIONS Interpretation of the ICP pulse waveform may be clinically useful in patients suffering from hydrocephalus. Elevated amplitude seems to be a positive predictor for clinical improvement after shunting. A properly functioning shunt reduces the pulse amplitude.

Apathy, ventriculomegaly and neurocognitive improvement following shunt surgery in normal pressure hydrocephalus

Introduction. Apathy – impaired motivation and goal-directed behaviour – is a common yet often overlooked symptom in normal pressure hydrocephalus (NPH). Caudate atrophy often yields apathetic symptoms; however, this structural and functional relationship has not yet been explored in NPH. Additionally, little is known about the relationship between apathy and post-shunt cognitive recovery. Methods. This audit investigated whether apathetic symptoms improve following shunt surgery in NPH, and whether this relates to cognitive response. In addition, we assessed the relationship between ventriculomegaly and apathy using the bicaudate ratio. Twenty-two patients with NPH completed the Mini-Mental State Examination (MMSE), the Apathy Evaluation Scale (AES) and the Geriatric Depression Scale (GDS) before and 3–9 months after shunt surgery. Pre-operative ventriculomegaly was correlated with pre-operative AES and GDS scores. Difference scores (post-shunt minus baseline values) for AES and GDS were correlated with cognitive outcome. Results. Greater pre-operative ventriculomegaly was associated with increased level of apathy and depression. A reduction in apathetic symptoms following shunt surgery was associated with improved performance on the MMSE. Conclusions. Apathy may be indicative of a greater degree of subcortical atrophy in NPH and may relate to functional outcome.

Neurosurgical history: comparing the management of penetrating head injury in 1969 with 2005

Penetrating head trauma may present challenging problems in the acute phase (removal of foreign bodies, control of haemorrhage, prevention of infection) and in the management of long-term sequelae (neurological deficit, cognitive impairment, seizures). Two unusual cases demonstrate the progress made in emergency medicine, radiology neurointensive care, and neurosurgical head injury management over 36 years.

Relationship between CSF dynamics and outcome after shunting in NPH- 20 years of single centre experience

Objective The strict relationship between shunt-responsiveness and increased resistance to CSF outflow (Rout) as reported in 1981 by Borgensen and Gjerris [1] was later presented as significant but not strong in the‘Dutch NPH’ trial [2] and recently reported as unconvincing in the ‘European NPH study’ [3]. We reviewed our ongoing database to study the relationship between parameters describing CSF circulation and pressure-volume compensation with clinical improvement after shunting.