Authors: Tomoya Sofue, Megumi Chatani, Norio Miyoshi, Kenkichi Takahashi, Shinji Yamamoto, Yoshihiro Kuga, Hiroyuki Ohnishi
Categories: Case Lesson, normal pressure hydrocephalus, lumboperitoneal shunt, subcutaneous emphysema, complication, LP = lumboperitoneal, NPH = normal pressure hydrocephalus, SAH = subarachnoid hemorrhage, VP = ventriculoperitoneal
Source: Journal of Neurosurgery: Case Lessons
Doi: 10.3171/CASE25584
Authors: Tomoya Sofue, Megumi Chatani, Norio Miyoshi, Kenkichi Takahashi, Shinji Yamamoto, Yoshihiro Kuga, Hiroyuki Ohnishi
Secondary normal pressure hydrocephalus is a common complication in the chronic phase after subarachnoid hemorrhage or intracerebral hemorrhage, with an incidence of approximately 30%. Lumboperitoneal (LP) shunts are often selected for older patients due to their less invasive nature. However, postoperative complications such as infection, catheter malfunction, and subdural hematoma are known.
The authors present the first known case of symptomatic subcutaneous emphysema following LP shunt surgery, necessitating reoperation. The patient was a markedly thin woman (BMI 13.3), and the cause of the complication was determined to be a combination of shallow subcutaneous catheter placement and failure to evacuate retained air prior to closure.
In thin patients, LP shunt catheters should be placed in deeper layers to minimize dead space and prevent air retention. In addition, care must be taken to release subcutaneous air before wound closure, especially in procedures performed in the lateral decubitus position.
https://thejns.org/doi/10.3171/CASE25584
Secondary normal pressure hydrocephalus (NPH) is a significant complication frequently encountered in the chronic phase following subarachnoid hemorrhage (SAH) or intracerebral hemorrhage. Its incidence is reported to be approximately 30%.^1^ Surgical intervention, typically involving either a ventriculoperitoneal (VP) or lumboperitoneal (LP) shunt, is the standard treatment. Nevertheless, complications such as catheter dysfunction, infection, and overdrainage-related subdural hematoma have been documented.^2^^,^^3^ Here, we report the first known case of symptomatic subcutaneous emphysema following LP shunt surgery, which required reoperation. We discuss the underlying pathophysiology, surgical pitfalls, and technical considerations.
A 74-year-old woman with no prior medical history presented with headache and impaired consciousness. She was diagnosed with SAH due to rupture of a dissecting aneurysm of the left vertebral artery (Hunt and Hess grade IV, World Federation of Neurosurgical Societies grade IV). Parent artery occlusion was performed with preservation of the posterior inferior cerebellar artery (Fig. 1A and B). Her postoperative course was favorable, and she was discharged home on postoperative day 40 with a modified Rankin Scale score of 1. However, after returning home, she developed urinary incontinence and gait disturbance. A tap test was performed with removal of 30 mL of CSF via lumbar puncture. Posttest evaluations showed improved gait speed, gait pattern, and cognitive scores on the Timed Up and Go test and the Mini–Mental State Examination. Her opening CSF pressure was 13 cm H2O. Imaging revealed enlargement of the lateral ventricles with an Evans index of 0.43 (Fig. 1C). Based on these findings, a diagnosis of secondary NPH was made, and LP shunt placement was planned. Preoperative abdominal CT revealed no obvious abnormalities (Fig. 1D).
FIG. 1.SAH due to rupture of a dissecting aneurysm of the right vertebral artery. A and B: Parent artery occlusion was performed, preserving the origin of the posterior inferior cerebellar artery. **C:**Axial head CT scan obtained 40 days after onset, demonstrating ventricular enlargement, leading to a diagnosis of secondary NPH. **D:**Preoperative abdominal CT scan showing no apparent abnormalities in either the intraperitoneal or extraperitoneal compartments.
Under general anesthesia, the patient was positioned in the right lateral decubitus position. Three skin incisions (3 cm on the lower back, 1 cm on the left flank, and 4 cm on the left paraumbilical region) were made (Fig. 2). With the lumbar spine slightly flexed, a lumbar puncture at the L2–3 level was performed. CSF outflow was confirmed, and a spinal catheter was inserted to a depth of 20 cm with satisfactory CSF drainage. A subcutaneous pocket was created via the dorsal incision for valve placement. A passer was used to create a subcutaneous tunnel from the flank to the abdominal region. After completing the lumbar portion, the legs were extended and the operating table tilted 15° to facilitate abdominal access. A transverse paraumbilical incision was made, and the peritoneal cavity was accessed via a transrectus approach. A 30-cm distal catheter was inserted into the peritoneal cavity. Layered closure was peritoneum with purse-string sutures, posterior and anterior rectus sheaths and dermis with absorbable sutures, and skin with surgical staples. FIG. 2.Intraoperative positioning with skin incisions (yellow arrows) made in the lumbar region, flank, and paramedian abdominal area.
Although emergence from anesthesia was uneventful, the patient reported abdominal pain and abdominal tightness on return to the ward. Examination revealed marked distension from the left flank to the left anterior abdominal wall. Abdominal CT demonstrated extensive subcutaneous emphysema along the shunt tract (Fig. 3). Although bowel injury was initially suspected, no signs of free air, intraperitoneal hemorrhage, or ileus were observed. Reoperation was performed because bowel injury could not be definitively ruled out, and manual abdominal compression was found to be insufficient for evacuating the trapped air. On incising the dermis, air was forcefully released from the deep tissues, resulting in immediate relief of pain and abdominal distention. No evidence of bowel injury was found. The flank was compressed inward to reduce dead space, and the catheter was carefully advanced into the peritoneal cavity to remove slack. Repeat CT confirmed resolution of the subcutaneous emphysema (Fig. 4A and B). Follow-up abdominal CT on the day after surgery showed further improvement of the subcutaneous emphysema (Fig. 4C and D). The patient remained symptom free and was discharged home on postoperative day 7. At the outpatient follow-up 3 weeks postoperatively, the subcutaneous emphysema had completely resolved (Fig. 4E and F). Written informed consent was obtained from the patient for publication of this case report and accompanying images. FIG. 3.Postoperative abdominal CT scans. A and B: Significant subcutaneous emphysema is seen, with subcutaneous tissue elevated by the shunt catheter and extensive air distribution between the subcutaneous layer and abdominal wall musculature, extending from the anterior abdomen to the flank and back. C and D: In more caudal slices, air was also noted within the external oblique and rectus abdominis muscles, with apparent muscle swelling. No evidence of bowel injury or intra-abdominal hemorrhage was observed. FIG. 4.Abdominal CT scans obtained after reoperation. **A and B:**Partial reduction in subcutaneous emphysema is seen. C and D: By the 1st postoperative day, subcutaneous air had largely resolved. **E and F:**By 3 weeks postoperatively, it had completely disappeared.
The necessary informed consent was obtained in this study.
Secondary NPH is a well-documented complication following hemorrhagic stroke, with a reported incidence of approximately 30%.^1^ In hemorrhagic stroke, the precise mechanisms leading to hydrocephalus remain incompletely understood; however, it is generally attributed to impaired CSF absorption caused by the influx of blood components into the subarachnoid space and ventricles.^4^ Surgical treatment with either a VP or LP shunt is standard practice. The SINPHONI-2 trial demonstrated that LP shunts are not inferior to VP shunts in terms of symptomatic improvement and adverse event rates, leading many institutions, including ours, to favor LP shunts in older patients for their minimally invasive nature.^2,^^3^ According to recent reports, postoperative complications following LP shunt placement occur in 7.0%–8.1% of cases within the 1st year. These include catheter malfunction (0.6%–4%), infection (2.5%), radiculopathy (1.2%), and overdrainage-related subdural hematoma (2.3%–3.4%). Although bowel injury was not observed in the present case, it remains an important complication that should be considered.^2^^,^^3^
Although minor subcutaneous emphysema is occasionally noted after LP shunt procedures, we found no prior reports of symptomatic subcutaneous emphysema requiring reoperation. In this case, a markedly emaciated patient (BMI 13.3) developed extensive symptomatic emphysema along the shunt tract. Imaging confirmed subcutaneous air without signs of visceral perforation. Reoperation revealed trapped air in the subcutaneous space, which was promptly evacuated. The presumed cause was 1) superficial placement of the shunt tubing in a thin patient with minimal subcutaneous tissue, creating a large potential space; and 2) failure to adequately evacuate air from the subcutaneous tract prior to wound closure, particularly in the lateral decubitus position because air tends to accumulate and is less likely to be evacuated in enclosed spaces where the superior (ceiling-facing) side is sealed. To our knowledge, this is the first reported case of symptomatic subcutaneous emphysema following LP shunt placement. Two key technical factors likely contributed to its 1) shallow catheter placement in a severely thin patient, leading to excess dead space; and 2) incomplete evacuation of air during closure, exacerbated by the lateral decubitus positioning (Fig. 5). To prevent this complication, surgeons should place shunt tubing in deeper subcutaneous layers, particularly in patients with low BMI, to reduce the risk of dead space and air entrapment. Additionally, meticulous attention should be paid to ensuring all residual air is evacuated before skin closure, especially in procedures performed in lateral positions where trapped air is less likely to escape spontaneously. We believe that the more prominent subcutaneous emphysema on the ventral side, as compared with the dorsal side, was attributable to the larger extent of the abdominal incision, highlighting that larger wounds may facilitate greater air entry. Confirming that the catheter is neither kinked nor excessively loose is also critical for both short- and long-term shunt functionality. This case underscores the importance of adapting surgical techniques to patient body habitus and reinforces the need for vigilance in managing air entrapment during closure. While rare, such complications can lead to significant patient discomfort and necessitate reoperation if not properly addressed. Some clinicians may find it difficult to believe that such a complication could occur; however, this very improbability underscores the importance of reporting the case. We hope that this will be not only the first but also the last reported case of this complication. FIG. 5.The shunt catheter created a redundant loop (red line), lifting the thin subcutaneous tissue and forming a space where air remained trapped (red arrows). As the air was not actively evacuated before closure, marked subcutaneous emphysema persisted postoperatively.
This case illustrates a first reported complication of LP shunt symptomatic subcutaneous emphysema requiring reoperation. In patients with very low BMI, shallow catheter placement can create excess space for air to accumulate. If air is not fully evacuated, especially in the lateral position, it may become trapped and cause symptoms. Careful technique and attention to patient anatomy are essential to prevent this issue.
This case is the first reported instance of symptomatic subcutaneous emphysema following LP shunt placement. The likely causes were superficial catheter placement in an extremely thin patient and insufficient evacuation of subcutaneous air before wound closure. In patients with minimal subcutaneous tissue, dead space is more likely to form, allowing air to accumulate along the shunt tract. Lateral positioning during surgery may further trap air, especially if the flank wound is closed before abdominal air can escape. To prevent this complication, the catheter should be placed in deeper layers, slack should be minimized, and any trapped air should be actively released before closure. These steps are essential to avoid reoperation and maintain long-term shunt function.
The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.
Conception and Sofue. Acquisition of Yamamoto. Analysis and interpretation of Yamamoto, Ohnishi. Drafting the Sofue, Miyoshi, Ohnishi. Critically revising the Sofue, Ohnishi. Reviewed submitted version of Sofue, Kuga, Ohnishi. Approved the final version of the manuscript on behalf of all Sofue. Administrative/technical/material Sofue, Yamamoto. Study Sofue, Chatani, Takahashi, Yamamoto.
Tomoya Sofue: Ohnishi Neurological Center, Akashi, Hyogo, Japan. ndmc.41.st@outlook.jp.