Syndrome of the Trephined: Functional Improvement After Reconstruction of Large Cranial Vault Defects
In 1939, Grant and Norcross2 first described the syndrome of the trephined as a cluster of symptoms including dizziness, undue fatigability, vague discomfort at the site of the defect, feeling of apprehension and insecurity, mental depression and intolerance to vibration in the face of bone defects in the skull. This syndrome has been called various names including: “sinking skin flap syndrome,” “paradoxical herniation,” and “syndrome of the trephined.”3,4 Currently, it is defined as a neurological deterioration or behavioral disturbance after craniectomy with reversibility of symptoms following reconstructive cranioplasty.5 Although this syndrome has been defined and is accepted as a true entity, it is often underdiagnosed by clinicians (Table 1).
Annan et al theorized that these neurological symptoms occur via direct transmission of atmospheric pressure to the intracranial cavity through the skin flap causing direct brain compression.3,5 This compression creates changes in cerebrospinal fluid (CSF) hydrodynamics, such as hypovolemia and hypopressure, which in turn leads to compression of cerebral vasculature, venous return impairment, and deformity of intracranial structures. This decrease in regional cerebral blow flow as seen on computed tomography (CT) scans, CT perfusion studies, Xenon CT, and magnetic resonance spectroscopy creates metabolic derangements leading to cortical dysfunction and the symptoms associated with the syndrome of the trephined.6–8
Patients are predisposed to these neurologic changes after undergoing a large craniectomy for pathologic entities including trauma, infarction, hemorrhage, and infection.4,5,9 Presenting symptoms of the syndrome include weakness, hemiparesis, paralysis, headaches, sensory changes, slowing of speech, impaired mentation, and gait disturbances.9 Patients can either present with acute neurologic deterioration or chronic neurologic impairment. Acute neurologic symptoms can be seen in patients with quick orthostatic positioning changes or after procedures that decrease CSF volume, such as lumbar puncture or ventriculoperitoneal shunt. The remaining subset of patients present as an arrest or regress in their neurorehabilitation, which is a more subtle presentation that can result in a delay in diagnosis. Patients can then be further evaluated with a CT scan of the head, which may demonstrate a sunken skin flap, midline shift, and ventricular effacement.5 Although most reports in the literature on the syndrome of the trephine are only of individual patients, there are consistent findings. The incidence is estimated between 1.2% and 24% of all patients following craniectomy.5,10 Ashayeri et al11 noted, in their systematic review, an average onset of symptoms at 5 months after craniectomy, albeit with a range from 3 days to 7 years. The most common symptom is motor weakness followed by cognitive deficits. Their review found that the syndrome is seen more frequently in males as well as in patients with a history of neurotrauma. An exact correlation between craniectomy size and patients with syndrome of trephined was not described in the literature, but they reported the average size for patients with the syndrome to be 88.3 cm2.11
The treatment and timing for syndrome of the trephined varies by practitioner and institution. When a patient with syndrome of the trephined is seen in the office for initial evaluation, there is a way to test if a cranial vault reconstruction is likely to improve, or even completely reverse, symptoms.