From the Guidelines
The significance of extra-axial fluid spaces lies in their potential to indicate various pathological conditions, such as subdural hematomas, hydrocephalus, or brain atrophy, which can affect intracranial pressure and cerebral perfusion pressure, as suggested by individualized management objectives 1. When evaluating extra-axial fluid spaces, it is essential to consider the patient's clinical context, including age, neurological symptoms, and head circumference.
- The extra-axial fluid spaces, including the subarachnoid space, subdural space, and epidural space, play a crucial role in cushioning the brain and facilitating cerebrospinal fluid (CSF) circulation.
- Abnormally enlarged extra-axial fluid spaces can be due to various conditions, such as benign enlargement of subarachnoid spaces (BESS), subdural hematomas, hydrocephalus, or brain atrophy, which may require different management approaches, including postoperative intracranial pressure (ICP) monitoring after evacuation of post-traumatic intracranial haematoma 1.
- In the context of traumatic brain injury, the incidence of postoperative intracerebral haematoma and uncontrollable intracranial hypertension highlights the importance of monitoring extra-axial fluid spaces for potential complications, such as secondary bleeding or increased brain oedema 1.
- The clinical significance of extra-axial fluid spaces is further emphasized by the need to distinguish normal developmental variants from pathological conditions that might require treatment, as the presence of fluid in these spaces can affect the brain's protection, CSF circulation, and potentially neurological function.
- In clinical practice, individualized management objectives for intracranial pressure and cerebral perfusion pressure should be considered, particularly in the first 24 hours after severe traumatic brain injury, as suggested by the study published in Anaesthesia in 2018 1.
From the Research
Significance of Extra-Axial Fluid Spaces
The significance of extra-axial fluid spaces can be understood by examining their role in various neurological conditions. Extra-axial fluid collections are known consequences of decompressive hemicraniectomy 2. These collections can be caused by a variety of factors, including surgical procedures, trauma, and infections.
Causes and Pathophysiology
The pathophysiology of postoperative extra-axial cerebrospinal fluid (CSF) collections involves the accumulation of CSF in the subarachnoid space, leading to increased intracranial pressure 3. This can occur due to a wide dissection and opening of the arachnoid membrane, resulting in a communication between the basal cisterns and the subdural space. The incidence of extra-axial collections after decompressive hemicraniectomy following ischemic stroke was lower in one retrospective series than has been reported by others 2.
Clinical Management
The clinical management of extra-axial fluid collections is crucial to prevent further complications. Ventriculoperitoneal (V-P) shunting has been shown to be an effective procedure in preventing progression and treating postoperative extra-axial CSF collections 3. In some cases, early anticipatory, corrective treatment with cerebrospinal fluid diversion or cranioplasty may not be warranted, as the collections may resolve spontaneously 2.
Key Findings
Some key findings related to extra-axial fluid spaces include:
- The ratio of intracranial CSF volume to brain volume can be used to assess the dynamics of intracranial volume changes in patients with space-occupying masses 4.
- Subdural fluid accumulation can be caused by ventriculoperitoneal shunt underdrainage, leading to a rare and paradoxical complication 5.
- Extra-axial fluid collections after decompressive craniectomy can be managed with a treatment algorithm that involves replacing the bone flap as soon as it is safe to do so and draining refractory collections aggressively 6.
Implications
The implications of extra-axial fluid spaces are significant, as they can affect patient outcomes and treatment strategies. Understanding the causes, pathophysiology, and clinical management of extra-axial fluid collections is essential to provide optimal care for patients with neurological conditions. Further studies are needed to assess long-term clinical outcomes of extra-axial fluid collections and to develop standardized management protocols 6.