Comparison Between Flow-Regulated and Gravitational Shunt Valves in the Treatment of Normal Pressure Hydrocephalus: Flow-Grav Study

Neurosurgery 89:413–419, 2021

Normal pressure hydrocephalus (NPH) is frequently treated with ventriculoperitoneal shunt (VPS) surgery. However, VPS implantation can lead to overdrainage and complications such as headaches, hygroma, and subdural hematoma due to a siphon effect in an upright position. Gravitational valves prevent overdrainage through positiondependent adjustment of valve resistance. Flow-regulated valves that increase resistance in presence of high cerebrospinal fluid flow may provide similar protection against overdrainage and present an alternative to gravitational valves.

OBJECTIVE: To compare gravitational and flow-regulated shunt valves in patients with symptomatic NPH.

METHODS: We performed a retrospective analysis of 97 patients suffering from NPH who underwent VPS implantation with a gravitational or a flow-regulated valve. The primary endpoint was the occurrence of hygroma or subdural hematoma. Secondary endpoints were neurological outcome (Kiefer score, Stein and Langfitt score, and NPH recovery rate), frequency of valve adjustments, and reoperations.

RESULTS: No significant differences in the occurrence of hygroma and subdural hematoma (11.4% for flow-regulated valves vs 5.7% for gravitational valves, P = .462) or response to treatment (77.3% vs 81.1%, P = .802) were found. Patients with flow-regulated valves required fewer valve adjustments (1.12 vs 2.02, P < .001) to reach their optimal neurological outcome and underwent fewer surgical revisions (11.4% vs 28.3%, P = .047).

CONCLUSION: Our data suggest that shunt therapy in NPH patients with a flow-regulated instead of a gravitational valve is safe and effective with a comparable clinical outcome and risk of overdrainage complications. Moreover, patients with flow-regulated valves may need fewer valve adjustments and reoperations.

Dynamic stabilization adjacent to single-level fusion: Part II. No clinical benefit for asymptomatic, initially degenerated adjacent segments after 6 years follow-up

Eur Spine J (2010) 19:2181–2189 DOI 10.1007/s00586-010-1517-4

Progression of degeneration is often described in patients with initially degenerated segment adjacent to fusion (iASD) at the time of surgery. The aim of the present study was to compare dynamic fixation of a clinically asymptomatic iASD, with circumferential lumbar fusion alone.

60 patients with symptomatic degeneration of L5/S1 or L4/L5 (Modic C 2) and asymptomatic iASD (Modic = 1, confirmed by discography) were divided into two groups. 30 patients were treated with circumferential single-level fusion (SLF). In dynamic fixation transition (DFT) patients, additional posterior dynamic fixation of iASD was performed. Preoperatively, at 12 months, and at a mean follow-up of 76.4 (60–91) months, radiological (MRI, X-ray) and clinical (ODI, VAS, satisfaction) evaluations assessed fusion, progression of adjacent segment degeneration (PASD), radiologically adverse events, functional outcome, and pain.

At final follow-up, two nonfusions were observed in both groups. 6 SLF patients and 1 DFT patient presented a PASD. In two DFT patients, a PASD occurred in the segment superior to the dynamic fixation, and in one DFT patient, a fusion of the dynamically fixated segment was observed. 4 DFT patients presented radiological implant failure. While no differences in clinical scores were observed between groups, improvement from pre-operative conditions was significant (all p<0.001). Clinical scores were equal in patients with PASD and/or radiologically adverse events. We do not recommend dynamically fixating the adjacent segment in patients with clinically asymptomatic iASD. The lower number of PASD with dynamic fixation was accompanied by a high number of implant failures and a shift of PASD to the superior segment.

Decompression of Chiari malformation with and without duraplasty: morbidity versus recurrence

J Neurosurg Pediatrics 5:474-478, 2010. DOI: 10.3171/2010.1.PEDS09218

The optimal surgical management of Chiari malformation (CM) is evolving. Evidence continues to accrue that supports decompression without duraplasty as an effective treatment to achieve symptomatic relief and anatomical decompression. The risks and benefits of this less invasive operation need to be weighed against decompression with duraplasty.

Methods. The authors performed a retrospective review of all CM decompressions from 2003 to 2007. All operations were performed by a single surgeon at a single institution. Data were analyzed for outcome, postoperative morbidity, and recurrence.

Results. Of 121 unique patients, 56 underwent posterior fossa decompressions without duraplasty (PFD) and 64 patients underwent posterior fossa decompressions with duraplasty (PFDD). Of the 56 PFD patients, 7 (12.5%) needed a subsequent PFDD for symptomatic recurrence. Of the 64 patients who underwent a PFDD, 2 (3.1%) needed a repeated PFDD for symptomatic recurrence. Patients treated with PFDD had an average operative time of 201 minutes in contrast to 127 minutes for those who underwent PFD (p = 0.0001). Patients treated with PFDD had average hospital stays of 4.0 days, whereas that for patients treated with PFD was 2.7 days (p = 0.0001). While in the hospital, patients treated with PFDD used low-grade narcotics, intravenous narcotics, muscle relaxants, and antiemetic medications at statistically significant differing rates.

Conclusions. While PFD was associated with a higher rate of recurrent symptoms requiring repeated decompression, this may be justified by the significantly lower morbidity rate. Clearer delineation of the trade-off between morbidity and recurrence may be used to help patients and their families make decisions regarding care.