From the Guidelines
A subdural hygroma is a collection of cerebrospinal fluid (CSF) that accumulates in the space between the brain and its outer covering, the dura mater, often associated with intracranial hypotension and CSF leakage. Unlike subdural hematomas which contain blood, hygromas consist of clear, watery CSF. They typically develop after head trauma, brain surgery, or from tears in the arachnoid membrane that allow CSF to leak into the subdural space, as seen in cases of spontaneous intracranial hypotension (SIH) 1. Many subdural hygromas are asymptomatic and resolve on their own without treatment. However, larger hygromas can cause symptoms similar to other brain injuries, including headaches, confusion, drowsiness, seizures, or focal neurological deficits depending on their size and location.
According to the most recent guidelines, treatment depends on severity - small, asymptomatic hygromas are often monitored with serial imaging, while larger symptomatic ones may require surgical drainage through burr holes or a craniotomy, in conjunction with treating the underlying CSF leak 1. The distinction between hygromas and chronic subdural hematomas can sometimes be challenging on imaging, as hygromas may evolve into hematomas over time if small blood vessels tear during the process. It is essential to investigate the possibility of spinal CSF leak in patients with subdural haematoma/hygromas, particularly those with a high index of suspicion such as supportive history of orthostatic headache, or absence of trauma/coagulopathy/alcohol misuse, using MRI of the brain with contrast and whole spine 1.
Key considerations in the management of subdural hygromas include:
- Monitoring for symptoms and signs of increased intracranial pressure or brain herniation
- Serial imaging to assess the size and evolution of the hygroma
- Investigation for underlying CSF leak and treatment of the leak source
- Surgical drainage for symptomatic hygromas with significant mass effect
- Conservative management for small or asymptomatic hygromas, while treating the underlying CSF leak 1.
From the Research
Definition of Subdural Hygroma
- A subdural hygroma is an accumulation of cerebrospinal fluid (CSF) in the subdural space, which can occur after head injury, trauma, or for iatrogenic reasons such as a lumbar puncture 2, 3.
- It can also be associated with spontaneous intracranial hypotension headache, meningitis, and other conditions 4.
Causes and Risk Factors
- Traumatic subdural hygroma (TSHy) is considered a benign epiphenomenon of trauma, but its pathogenesis is still unclear 2.
- Risk factors for developing subdural hygroma after decompressive craniectomy in patients with traumatic brain injury include midline shift, subarachnoid hemorrhage, delayed hydrocephalus, compression of basal cisterns, and tearing of the arachnoid membrane 5.
- Spinal subdural hygroma is a rare entity that can be associated with trauma, iatrogenic causes, and other conditions 4.
Diagnosis and Treatment
- Diagnosis of subdural hygroma is typically made using CT or MR imaging, with MR imaging being the golden standard for diagnosis of spinal subdural hygroma 4.
- Treatment of subdural hygroma is often conservative, with surgery seldom necessary, but treating the underlying cause is important 4, 6.
- In some cases, subdural hygroma can resolve spontaneously, as seen in a case report of a patient with aneurysmal subarachnoid hemorrhage 6.