When the news got out that Edison was developing the first practical electric light bulb, not everyone was impressed. A British Parliament Committee noted that Edison's light bulb was "unworthy of the attention of practical or scientific men" and a chief engineer for the British Post Office said that the "subdivision of the electric light is an absolute ignis fatuus." In other words, a fairy tale. A sham.
Key point:
- To evaluate the effect of MMA embolization on cronic subdural hematoma (cSDH) and to compare outcomes of the endovascular treatment (EVT) and the conventional treatment.
Yamashima's studies demonstrated that there is no clear plane between the dura and arachnoid in situ and that instead of the virtual subdural space, there is a dura-arachnoid interface layer.
In subdural hematoma, an extravasation of blood within the dural border layer splits it, leaving a few tiers of dural border cells over the arachnoid. These cells cover the internal surface of the hematoma, proliferate, and later on, form the inner membrane. However the outer membrane is related to hematoma enlargement because of the repetitive hemorrhages of the middle meningeal arterial branches located inside. It means that in theory, embolization of the middle meningeal artery (MMA), can control bleeding from the CSDH membrane and eventually enhance spontaneous resolution of the hematoma.
In fact, initial case reports and more recently several clinical studies have shown the efficacy of endovascular middle meningeal artery (MMA) embolization in treating CSDH. That is why Srivatsan A. et al. presented a systematic review to assess safety and outcomes of EVT compared with conventional surgical therapies.
The first thing evident is that of all the variables analyzed, percentage of patients on antiplatelet or anticoagulant therapy proved to be different (40.6% in EVT vs. 25.1% in conventional treatment). Antiplatelet or anticoagulant therapy is not a contraindication for EVT and discontinuation or reversal of these drugs would be unnecessary in patients undergoing EVT. Conceptually, these patients should have a higher risk of recurrence, and this may further point to efficacy of MMA embolization.
Moreover, the composite recurrence rates of 2.1% for the EVT across the 3 double-arm studies ( 3.6% across the 6 single-arm case series) is much lower than the recurrence rates reported in the literature conventional neurosurgical treatment, despite no statistically significant difference has been reported for complication rates.
cSDH can present heterogeneously, and symptom onset and progression can vary from days to weeks. Presentation can occasionally mimic stroke or rapidly progressive dementia. In terms of level of consciousness, 81% of patients have a presenting Glasgow Coma Scale (GCS) score of 13–15, 12% a GCS score of 9–12, and only 7% a GCS score of ≤8. This means that for each patient consideration needs to be given as to whether urgent surgery is required (e.g. patients with severe symptoms and/or large collections) or nonoperative management can be pursued (e.g. patients with mild symptoms and/or small collections), despite generally it is a strategical failure.
Moreover, multiple standard surgical techniques exist for the evacuation of cSDH:
- twist drill craniostomy (TDC), that produce the smallest openings of the skull (<10 mm)
- burr-hole craniostomy (BHC), that enable larger openings (<30 mm in diameter)
- craniotomy with the removal of a substantial piece of bone (>30 mm)
In all these techniques there are high rates of recurrence or reoperation and complications.
It suggests that:
- in asymptomatic patients the EVT could be an alternative to the “nonoperative management”;
- in symptomatic patients who require a urgent surgery it is not an alternative to the neurosurgical treatment, but it could be and an adjunctive treatment in order to avoid recurrences.
And this flowchart could represent the future of the treatment of cSDH.
In conclusion:
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The course of CSDH is determined by a balance of bleeding and absorption through its membrane and spontaneous resolution occurs less commonly, which suggests that a more active approach than simple close follow-up is needed. The EVT could be useful particularly in groups of patients who can potentially deteriorate quickly: younger patients (usually <65 years) who present with headaches but no or minimal neurological deficits and patients with sizeable bilateral collections, which, if of similar size, may cause no midline shift but can still exert substantial mass effect.
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The current surgical treatment cannot resolve the underlying pathophysiologic conditions.
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MMA embolization followed by hematoma removal can be a better strategy for patients with CSDHs requiring surgical hematoma removal for symptom relief.
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Cerebral infarction caused by the discontinuation of antiplatelet drugs or anticoagulation and acute epidural or subdural hematoma in patients with thrombocytopenia or residual effect of antiplatelet drugs despite platelet transfusion were the most common complications. Discontinuation or reversal of these drugs would be unnecessary in patients undergoing EVT.
Reference
- Yamashima T. The inner membrane of chronic subdural hematomas: pathology and pathophysiology. Neurosurg Clin N Am. 2000 Jul;11(3):413-24.
- Ducruet AF, Grobelny BT, Zacharia BE, et al. The surgical management of chronic subdural hematoma. Neurosurg Rev. 2012;35:155-169 [discussion: 169].
- Srivatsan A, Mohanty A, Nascimento FA, Hafeez MU, Srinivasan VM, Thomas A, Chen SR, Johnson JN, Kan P. Middle Meningeal Artery Embolization for Chronic Subdural Hematoma: Meta-Analysis and Systematic Review. World Neurosurg. 2018 Nov 24. pii: S1878-8750(18)32726-8. doi: 10.1016/j.wneu.2018.11.167. [Epub ahead of print]
Francesco Diana