Postoperative brain stem tension pneumocephalus causing transient locked-in syndrome

The vascular locked-in and locked-in-plus syndrome: A retrospective case series

The locked-in syndrome (LiS) is defined as the loss of most voluntary muscle movements with preserved cognitive abilities due to a ventral pontine lesion. However, some patients may also have severe impairment of consciousness [locked-in plus syndrome (LiPS)]. Here we aimed to explore structural differences between LiS and LiPS patients of vascular aetiology, focusing on lesion patterns and locations to better delineate the clinical spectrum of LiS and LiPS. In this retrospective case series study, we report nine patients (two women), ages 29-74 years (median 50) with LiS and LiPS who were diagnosed between 2007 and 2021. Clinical parameters, MRI findings including the lesioned structures, and a shape feature calculation are presented for every patient. The lesioned structures were determined by a senior neuroradiologist. Two of nine patients had fully retained consciousness (LiS) and seven showed various degrees of impaired consciousness (LiPS). Lesions of LiS patients are round and confined to the pons, whereas lesions of LiPS patients are more elongated and reach neighbouring areas such as the mesencephalon, thalamus or ascending reticular activating system. Lesions involving the mesencephalon and the thalamus are strong indicators of LiPS, whereas for lesions restricted to the pons, the dorsal extension and the associated damage to the ascending reticular activating system are crucial to differentiate LiS from LiPS. Recognizing LiPS using clinical and radiological findings is important as these patients may need different therapies and care and, most importantly, should not be mistaken as unresponsive wakefulness syndrome.

Locked-in syndrome revisited

The locked-in syndrome (LiS) is characterized by quadriplegia with preserved vertical eye and eyelid movements and retained cognitive abilities. Subcategorization, aetiologies and the anatomical foundation of LiS are discussed. The damage of different structures in the pons, mesencephalon and thalamus are attributed to symptoms of classical, complete and incomplete LiS and the locked-in plus syndrome, which is characterized by additional impairments of consciousness, making the clinical distinction to other chronic disorders of consciousness at times difficult. Other differential diagnoses are cognitive motor dissociation (CMD) and akinetic mutism. Treatment options are reviewed and an early, interdisciplinary and aggressive approach, including the provision of psychological support and coping strategies is favoured. The establishment of communication is a main goal of rehabilitation. Finally, the quality of life of LiS patients and ethical implications are considered. While patients with LiS report a high quality of life and well-being, medical professionals and caregivers have largely pessimistic perceptions. The negative view on life with LiS must be overthought and the autonomy and dignity of LiS patients prioritized. Knowledge has to be disseminated, diagnostics accelerated and technical support system development promoted. More well-designed research but also more awareness of the needs of LiS patients and their perception as individual persons is needed to enable a life with LiS that is worth living.

The semi-sitting position in patients with indwelling CSF shunts: perioperative management and avoidance of complications

OBJECTIVE

Posterior fossa or midline tumors are often associated with hydrocephalus and primary tumor removal with or without perioperative placement of an external ventricular drain (EVD) is commonly accepted as first-line treatment. Shunting prior to posterior fossa surgery (PFS) is mostly reserved for symptomatic cases or special circumstances. There are limited data regarding the anticipated risk for symptomatic pneumocephalus and the perioperative management using the semi-sitting position (SSP) in such a scenario. Here, we therefore assessed the safety of performing PFS in a consecutive series of patients over a period of 15 years to allow the elaboration of recommendations for perioperative management.

METHODS

According to specific inclusion and exclusion criteria a total of 13 patients who underwent 17 operations was identified. Supratentorial pneumocephalus was evaluated with semiautomatic-volumetric segmentation. The volume of pneumocephalus was evaluated according to age and ventricular size.

RESULTS

Ten of the 13 patients had a programmable valve (preoperative valve setting range 6-14 cmH20; mean 7.5 cmH20) while 3 patients had non programmable valves. A variable amount of supratentorial air collection was evident in all patients postoperatively (range 3.2-331 ml; mean 122.32 ml). Positive predictors for the volume of postoperative pneumocephalus were higher age and a preoperative Evans ratio > 0.3. In our series, we encountered no cases of tension pneumocephalus necessitating an air replacement procedure as well as no obstruction, disconnection, infection or hardware malfunction of the shunt system.

CONCLUSIONS

Our findings indicate that a CSF shunt in situ is not a contraindication for performing PFS in the semi-sitting position and it does not increase the pre-existing risk for postoperative tension pneumocephalus. In cases of primary shunting for hydrocephalus associated with posterior fossa tumors a programmable valve set at a medium opening pressure with a gravitational device is a valid option when PFS in the semi-sitting position is opted. In patients with an indwelling shunt diversion system special caution is indicated in order to prevent and detect overdrainage especially in not adjustable valves or shunts without antisiphon devices.

Pneumocephalus after posterior fossa surgery in prone position: Is that any clinical effect?

Introduction

The term pneumocephalus refers to the existence of air in any intracranial compartment. Its presence in the follows of a supratentorial craniotomy is very common, and it usually represents a benign complication as it is very rarely responsible for clinical manifestations.

Case presentation

We report the case of a 24 years-old man, who underwent posterior fossa surgery in prone position for resection of a vermian tumor. Postoperative, the patient presented a tonic-clonic generalized seizure associated to high levels of arterial pressure and decerebration. Control CT scan showed an important pneumocephalus. On the posterior fossa, the air was responsible for a compression of the brainstem, without any other postoperative complications. Following 12 h of conservative management, a brain MRI showed a total regression of the pneumocephalus. 3 days later, the patient presented a favorable outcome as he was extubated without any major impairments.

Discussion

Transformation of pneumocephalus into tension pneumocephalus responsible for clinical inadvertance is rare. This complication is mainly related to surgeries performed in sitting position. The occurrence of compressive pneumocephalus after a posterior fossa craniotomy performed in a prone position is seldom.

Conclusions

Through this case, we discuss pathophysiology and therapeutic approaches for tension pneumocephalus following posterior fossa performed in prone position.

•

Pneumocephalus may be source for major postoperative inadvertance

•

Tension pneumocephalus was reported in supratentorial surgeries. Posterior fossa craniotomies may also lead to this inadvertence.

•

Rigorous peroperative prevention of pneumocephalus should be considered in order to minimize complications.

Normobaric hyperoxia for treatment of pneumocephalus after posterior fossa surgery in the semisitting position: a prospective randomized controlled trial

Background

Supratentorial pneumocephalus after posterior fossa surgery in the semisitting position may lead to decreased alertness and other symptoms. We here aimed to prove the efficacy of normobaric hyperoxia on the absorption of postoperative pneumocephalus according to a standardized treatment protocol.

Methods and Findings

We enrolled 44 patients with postoperative supratentorial pneumocephalus (> 30 ml) after posterior fossa surgery in a semisitting position. After randomisation procedure, patients received either normobaric hyperoxia at FiO₂ 100% over an endotracheal tube for 3 hours (treatment arm) or room air (control arm). Routine cranial CT scans were performed immediately (CT1) and 24 hours (CT2) after completion of surgery and were rated without knowledge of the therapy arm. Two co-primary endpoints were assessed: (i) mean change of pneumocephalus volume, and (ii) air resorption rate in 24 hours. Secondary endpoints were subjective alertness (Stanford Sleepiness Scale) postoperatively and attention (Stroop test), which were evaluated preoperatively and 24 hours after surgery. The mean change in pneumocephalus volume was higher in patients in the treatment arm as compared to patients in the control arm (p = 0.001). The air resorption rate was higher in patients in the treatment arm as compared to patients in the control arm (p = 0.0015). Differences were more pronounced in patients aged 52 years and older. No difference between patients in treatment arm and control arm was observed for the Stroop test. The distribution of scores in the Stanford Sleepiness Scale differed in the treatment arm as compared to the control arm, and there was a difference in mean values (p = 0.015).

Conclusions

Administration of normobaric hyperoxia at FiO₂ 100% via an endotracheal tube for 3 hours is safe and efficacious in the treatment of pneumocephalus after posterior fossa surgery in the semisitting position. Largest benefit was found in elderly patients and particularly in older men.

Trial Registration

German Clinical Trials Register DRKS00006273

Is nitrous oxide use appropriate in neurosurgical and neurologically at-risk patients?

PURPOSE OF REVIEW

To address controversial issues surrounding the use of nitrous oxide as a component of anesthesia in neurosurgical and neurologically at-risk patients.

RECENT FINDINGS

Nitrous oxide has been used as a component of general anesthesia for over 160 years and has contributed to countless apparently uneventful anesthetics in neurologically at-risk patients. Avoidance of nitrous oxide in specific circumstances, such as pre-existing pneumocephalus, during acute venous air embolism, and in patients with disorders of folate metabolism, is warranted. However, various controversies exist regarding the use of this drug in the general neurosurgical population. Specifically, some suggest a possible association between nitrous oxide and the postoperative development of tension pneumocephalus despite lack of data to support this notion. Additionally, data describing alterations of cerebral hemodynamics and metabolism and exacerbation of ischemic neurologic injury by nitrous oxide are inconsistent. Recent data derived from humans having cerebral aneurysm clipping failed to show any long-term adverse effect from the use of nitrous oxide on gross neurologic or cognitive function.

SUMMARY

Except in a few specific circumstances, there exists no conclusive evidence to support the dogmatic avoidance of nitrous oxide in neurosurgical patients.

Cervical spinal cord infarction after posterior fossa surgery: a case-based update

BACKGROUND

Several positions are currently utilized for operating patients with posterior fossa lesions. Each individual position has its own risks and benefits, and none has demonstrated its superiority. A dreaded, and probably underreported, complication of these procedures is cervical cord infarction with quadriplegia.

DISCUSSION

We reviewed eight previous reported instances of this devastating complication aimed at ascertaining its pathogenesis to suggest preventive strategies. Several hypotheses have been put forward to explain the occurrence of this complication. Some factors involved in the production of cervical cord infarction include patient's position (seated or prone), hyperflexion of the neck, excessive spinal cord traction, canal stenosis, and systemic arterial hypotension. We hypothesize that spinal cord infarction in our patient might have resulted from compromised blood supply to the midcervical cord caused by tumor infiltration of the cervical leptomeninges in addition to a brief episode of arterial hypotension during venous air embolism.

CASE REPORT

We treated an 8-year-old girl who developed quadriplegia after surgery for a fourth ventricular ependymoma. Postoperative magnetic resonance imaging demonstrated cervical cord infarction. Evoked potentials confirmed the diagnosis.

CONCLUSIONS

With this report, we want to draw the attention of neurosurgeons to the possibility of the occurrence of this dreadful complication during posterior fossa procedures. Retrospectively, the only measures that might have helped to avoid this complication in our patient would have been using the prone position and intraoperative monitoring of evoked potentials.

Locked-in syndrome in children: report of five cases and review of the literature

The locked-in syndrome is a rare neurologic disorder defined by (1) the presence of sustained eye opening; (2) preserved awareness; (3) aphonia or hypophonia; (4) quadriplegia or quadriparesis; and (5) a primary mode of communication that uses vertical or lateral eye movement or blinking. Five cases are reported here, and previous literature is reviewed. According to the literature, the most common etiology of locked-in syndrome in children is ventral pontine stroke, most frequently caused by a vertebrobasilar artery thrombosis or occlusion. In terms of prognosis, 35% of pediatric locked-in syndrome patients experienced some motor recovery, 26% had good recovery, 23% died, and 16% remained quadriplegic and anarthric. These findings raise important ethical considerations in terms of quality of life and end-of-life decisions in such challenging cases.