From the Guidelines
Midline shift occurs in approximately 20-30% of patients with traumatic brain injuries requiring hospitalization, with shifts greater than 5mm associated with poorer prognosis and higher mortality rates. This complication is a serious consequence of severe head trauma, where brain tissue, blood, or cerebrospinal fluid accumulation causes the brain to shift from its normal centered position past the midline of the skull. The severity of midline shift directly correlates with patient outcomes, with shifts exceeding 10mm correlating with significantly higher mortality rates 1.
Causes and Risk Factors
The most common causes of midline shift include:
- Subdural hematomas (blood collecting between the brain and its outer covering)
- Epidural hematomas (bleeding between the skull and the dura)
- Intracerebral hemorrhages
- Significant cerebral edema (brain swelling) These conditions can lead to increased intracranial pressure, which can cause the brain to shift and result in further complications, such as brain herniation, permanent neurological damage, or death if not addressed quickly 1.
Diagnosis and Treatment
Prompt diagnosis through CT scanning is essential to identify midline shift and initiate immediate treatment. Emergency treatment typically involves measures to reduce intracranial pressure, including:
- Surgical interventions like hematoma evacuation, decompressive craniectomy
- Medical management with osmotic agents like mannitol or hypertonic saline Monitoring ICP after post-traumatic intracranial haematoma evacuation is also suggested in certain cases, such as preoperative Glasgow Coma Scale motor response inferior or equal to 5, preoperative anisocoria or bilateral mydriasis, or preoperative severity signs on cerebral imaging, including brain midline shift over 5 mm 1.
Prognosis and Outcomes
The incidence of high ICP varies between 17 and 88%, and an ICP of 20–40 mmHg is associated with a higher risk of mortality and poor neurological outcome 1. The presence of traumatic subarachnoid haemorrhage is also associated with a risk of intracranial hypertension, and the compression of basal cisterns appears to be the best sign to reflect intracranial hypertension 1. Therefore, prompt recognition and treatment of midline shift are crucial to improve patient outcomes and reduce morbidity and mortality.
From the Research
Incidence of Head Trauma with Midline Shift
- The incidence of head trauma with midline shift is a significant concern in traumatic brain injuries, with various studies investigating its pathophysiologic implications 2.
- A study published in 2000 found that midline shift after severe head injury is associated with reduced cerebral metabolic rate of oxygen (CMRO2), regardless of the presence of subdural hematoma (SDH) 2.
- Another study published in 2019 proposed a novel measurement of overall mid-surface shift, which quantifies the total volume of brain tissue shifted across the midline, and found it to have a stronger correlation with TBI patient outcomes compared to traditional midline shift 3.
- A 2021 study suggested that midline shift in patients with closed traumatic brain injury may be driven by cerebral perfusion pressure, not intracranial pressure, and found a significant correlation between interhemispheric noninvasive cerebral perfusion pressure (nCPP) difference and midline shift 4.
- Radiological and clinical criteria, including midline shift, have been established to guide the management of epidural hematomas in children, with a midline shift >4 mm being a significant predictor of surgical intervention 5.
Key Findings
- Midline shift is associated with reduced CMRO2 in traumatic brain injuries 2.
- Mid-surface shift has a stronger correlation with TBI patient outcomes compared to traditional midline shift 3.
- Cerebral perfusion pressure may be a driving force for midline shift in closed traumatic brain injury 4.
- Midline shift is a significant predictor of surgical intervention in the management of epidural hematomas in children 5.