The term paradoxical herniation was first used by Schwab et al. in 1998 [1], it is a rare, potentially life-threatening but treatable complication, with progressive neurologic deterioration, sunken skull defect, midline shift, and compression of the brainstem . It may present in a delayed fashion after a lumbar puncture in patients with DC, Vilela [2] explained the cause that with a large skull defect, a lumbar puncture exacerbates the negative pressure gradient between the atmosphere and the cranium. Large dose of mannitol administration may aggravate the situation. For treatment, patients should be treated with trendelenburg position, and clamping of CSF drainage, dehydration therapy should be discontinued instead of hyperosmolar with colloid [3, 4].

Oyelese A et al. [5] report a case of paradoxical herniation from intracranial hypotension secondary to a lumbar puncture. This patient developed a large right hemispheric stroke after suprasellar meningioma resection, immediate DC was performed to reduce intracranial hypotension. 1 month after decompressive hemicraniectomy the patient developed a large subgaleal and subdural hygroma, 4 days of LP (lumber acupuncture) was performed followed by sudden consciousness loss and bilateral pupil dilation, a huge dose of mannitol administration even worsen the situation. Fields et al. [6] report a patient 43 with a cerebral contusion and a subdural hematoma who underwent DC and medium pressure ventriculoperitoneal shunt. Two months later after an LP, his condition markedly deteriorated, a brain CT scan showed a mark with the midline shift in the direction opposite the craniectomy site with subfalcine herniation and effacement of the peripontine cisterns. Given the concern for paradoxical herniation, 5 h after his initial deterioration, he was placed in the trendelenburg position, intravenous fluids were administered, and the VPS was tied off, his condition improved within 1 h.

SDG is a kind of CSF hydrodynamic disturbances frequently caused by DC [7–11]. The contralateral SDG were constantly reported, the aetiology was thought to combine with external cerebral herniation. This outward herniation combined with rapid reduction in ICP may incite a pressure gradient between the two hemispheres and lead to the enlargement of the contralateral subdural space and the accumulation of effusion, especially when, initially, there is a possible rupture in the arachnoid layer after head trauma [12–14].

In this case, SDG harbored in the opposite side of midline shift besides the cranial defect has never been reported before. We supposed, the brain translocation caused by paradoxical herniation may be the initiating factors of this kind of SDG. Without the knowledge of paradoxical herniation, we could easily come to the wrong conclusion that the mass effect of SDG pushed the midline to the opposite site. If a borehole or lumbar acupuncture was performed to solve the SDG, the neurologic deterioration will continue because of the rising of paradoxical herniation and pressure imbalance after CSF lost [5]. Under the “do no harm” principle, patients with coexistent of paradoxical herniation and SDG without severe neurologic deterioration, could be tentatively given high dose of intravenous infusion, before we take any surgical treatment. But, for these patients with severe midline shift, the none-surgical therapy is untried and need further prove.