DISCUSSION:
ISH is a rare complication of spinal anesthesia. About 41 % of postpartum ISH becomes chronic and the ratio of acute (31%) and subacute (33%) subdural hematomas (SDH) are similar3.
While the exact incidence of ISH following spinal anesthesia is unknown, as patients are usually treated conservatively without any investigations and reporting, it is known that the incidence of intracranial subdural hematoma following this anesthesia is 1:500,000 – 1,000,000 5.
The mechanism of development of ISH following spinal anesthesia is analogous to PDPH. It is postulated that the orifice made in the dura mater after puncturing with the cerebrospinal fluid (CSF) needle, remains open for several weeks after the puncture. This leads to rapid loss of CSF which reduces the intraspinal and intracranial pressure. This causes a caudal shift of the brain, which causes traction of the structures sensitive to pain and bridging veins in the subdural space leading to its rupture causing ISH and headache 5,6. The time taken for diagnosis of ISH following a dural puncture ranges from 4 h to 29 weeks2,4.
The time that is taken from CSF loss to progress to headache and develop hematoma range from 2 hours to 44 days 5. Most often when physicians come upon a case of headache following spinal anesthesia, PDPH is assumed to be the cause 3,7. Headache due to PDPH worsens or develops within 15 minutes after sitting or standing up, and it improves within a similar period after laying down. It appears within 5 days after the puncture and resolves spontaneously within 1 week or up to 48 hours after epidural blood patch8,9. This distinguishing feature helps us to exclude other causes of postpartum headache. However, in rare situations, the headache may last for months or even years 10. ISH should be suspected in a patient when PDPH changes its characteristics to non-postural headache with possible accompanying features like focal central nervous system (CNS) signs, impairment in consciousness level, paresis, ptosis, vomiting, blurring of vision, drowsiness, disorientation, prolonged unresolved headache 1,6. Unlike these typical features, ISH may present only as a headache and may be unrelated to PDPH 8.
Postpartum headaches are quite common (39%) 4, majority of them are primary headaches such as (migraine, tension-type, and cluster headache) and are therefore considered first in the differential diagnosis 4. Secondary postpartum headache can be fatal and includes PDPH, eclampsia/pre-eclampsia, cerebral venous thrombosis, reversible cerebral vasoconstriction syndrome, pituitary mass/hemorrhage 4. It is common that these headaches coexist and simulate each other in the puerperium causing difficulty in differentiation 8.
Predisposing factors for ISH following spinal anesthesia are pregnancy, use of large-sized needles, multiple dural punctures dehydration, use of anticoagulants, cerebral vascular abnormalities, and brain atrophy1,2,9. Increased susceptibility during pregnancy may be due to differences in elasticity of the dura, hemostatic imbalance, and possibly gender-based differences in cranial morphology1. Due to venous dilatation in pregnancy intracranial vessels are prone to tear and bleed. Moreover, postpartum diuresis, peripartum dehydration which could decrease the amount of CSF, sudden reduction of intra-abdominal pressure, vena caval pressure at delivery, hormonally-induced ligamentous changes 3, Valsalva maneuver at labor 3,9, thrombocytopenia3,9 increases the susceptibility to develop cerebral SDH.
Diagnosis of ISH is usually made by a CT scan of the head. However, cranial Magnetic resonance imaging is more sensitive and specific for iso-dense CSDH 7. Surgery is indicated if the thickness of hematoma is more than 10 mm, midline shift is greater than 5 mm, or there is neurologic deterioration 4. In absence of the above features, conservative management is recommended which requires close neurological and radiological follow ups1,2. In addition, it is established that ISH caused by dural punctures resulting in long-standing CSF leakage can also be treated with epidural dural patching 4.
The incidence of ISH following spinal anesthesia and development of related complications is preventable to some extent, vigilance regarding procedure-related factors, prophylactic monitoring of susceptible patients, and regular follow-up after discharge help in avoiding potential morbidity and mortality6.
In the reported case the patient developed headache 13 days after LSCS. Her headache did not have an association with PDPH and other neurologic signs. As her symptoms were vague, there was a possibility of misdiagnosis. Perhaps, the development of CSDH in her case was chiefly due to the lumbar puncture during spinal anesthesia. Moreover, her post-pregnancy status may have added up as a predisposing factor for the progression of the CSDH.