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This is a 10-month-old male who sustained an unwitnessed fall off a patio deck. The height of the fall was estimated at 2-3 meters. He landed on a concrete surface. Relatives were nearby and immediately ran to the screaming child. There was no reported vomiting or seizure activity. On physical examination he was noted to be sleepy but easily arousable. There was echymosis and an abrasion over the right periorbital area. A 7 by 4 by 1 cm hematoma was palpated over the right parietal region. No Battle's sign was present. His pupils were equal and reactive to light and extraocular movements were intact. Tympanic membranes were intact without hemotympanum. He had no areas of tenderness, swelling, bruising or deformity over his trunk and extremities. A CT scan of his head was performed. View his CT scan. This CT scan shows an elevated right parietal skull fracture with a floating fracture fragment, subarachnoid hemorrhage, hemorrhagic contusion of the right parietal and occipital lobes and a right parietal subdural hematoma. He was hospitalized and treated conservatively with a good recovery. Three months after the fall he is now noted to have a palpable right parietal skull fracture defect with a 1 cm "gap" in the bone. No palpable, pulsatile masses are noted. On clinical exam, he does not have any neurologic defects. A skull series is ordered. View his skull films. These are his left and right lateral views of his skull which show a large "gap" with smooth edges consistent with a growing skull fracture over his right parietal skull region. A follow up CT scan of his head is ordered. View his follow up CT scan. These CT scan images demonstrate the persisting skull defect and an underlying encephalomalacic cystic defect which is consistent with a leptomeningeal cyst. He underwent a right craniotomy with dural repair. Discussion Simple skull fractures usually heal without incident within a few weeks. One potential complication is a "growing skull fracture". Although most commonly known as a growing skull fracture, it is also referred to as a leptomeningeal cyst or posttraumatic meningocele (1). The essential features of this condition are a skull fracture in infancy or early childhood, a dural tear at the time of fracture, brain injury beneath the fracture and subsequent enlargement of the fracture to form a cranial defect (2). The incidence of growing skull fractures is estimated at 1% among skull fractures in children. Growing skull fractures occur during the first 3 years of life and almost never after eight years of life (3). This is due to the rapid increases in brain growth seen only in infancy. Pathogenesis A dural laceration is an essential component of a growing skull fracture. The development of a growing skull fracture requires a fracture severe enough to include a tear in the underlying dura and an outward driving force such as a normally growing brain or hydrocephalus (1). Continued pulsation of the brain and arachnoid is thought to enlarge the fracture over time (4) and herniation of the cerebral tissue or subarachnoid fluid through the fracture line may occur. A leptomeningeal cyst represents an invagination and entrapment of arachnoid into a diastatic fracture with an associated dural tear (5). This prevents healing of the fracture margins, can cause expansion of the fracture and is a palpable mass on physical exam. Linear fractures most commonly are associated with growing skull fractures while depressed fractures are not. A fracture with a diastasis (separation) of more than 4 mm may be considered at risk of developing a growing fracture (3). Beneath the lesions of skull and dura matter there is local brain injury which is a constant feature of this syndrome (2) and on acute imaging studies there is usually an indication of a cortical injury immediately beneath the fracture (1). A growing skull fracture presents as a progressively enlarging pulsatile mass or an enlarging and sunken palpable cranial defect (6). It may enlarge over months and occur months after the initial skull fracture. Neurological complications related to growing skull fractures include seizures (often intractable), hemiparesis and psychomotor retardation (3). The majority of cases have shown progressively worsening neurologic deficits over time (6). Therefore, it is important to examine children with skull fractures 4-6 weeks post injury to ensure adequate healing at the site of the initial fracture. The most common location for the development of a growing fracture is the parietal bone, although it can occur anywhere, including the skull base (1). Skull radiographs taken at the time of the initial injury will universally demonstrate a diastatic fracture, with the edges separated by more than 3mm (6). Computed tomography is helpful in identifying underlying intracranial pathology. Imaging done at the time of trauma may show a hemorrhagic contusion or subarachnoid or extraparenchymal hemorrhage (3). CT scan done months after the injury may also demonstrate unilateral ventricular enlargement and a shift toward the skull defect (6). Early surgical correction is recommended due to the risk of neurological complications (seizures, hemiparesis). There is no indication that the condition ever improves spontaneously (6). Intractable seizures in association with a growing skull fracture often respond to surgical correction. Principles of surgery include reconstruction of the dura, reconstruction of the skull and excision of excessive scalp tissue (4). References: 1. Luerssen TG. Skull fractures after closed head injury. In: Albright AL, Pollack IF, Adelson PD (eds). Principles and Practice of Pediatric Neurosurgery. Thieme, New York, 1999, pp821-823. 2. Lende RA, Erickson TC. Growing skull fractures of childhood. Journal of Neurosurgery 1961;18:479-487. 3. Tomita T. Growing skull fractures of childhood. In: Wilkins RH, Rengachary SS (eds). Neurosurgery. McGraw Hill, New York, 1996, pp2757-2761. 4. Raffel L, Litofsky NS. Skull fractures. In: Cheek WR (ed). Pediatric Neurosurgery. WB Saunders Company, Philadelphia, 1994, p258. 5. Beckett WW, Ball WS. Craniocerebral trauma. In: Ball WS (ed). Pediatric Neuroradiology. Lippincott-Raven, Philadelphia, 1997, pp454-455. 6. Luerssen TG, Eisenberg HM, Levin HS. Late complications of head injury. In: Cheek WR (ed). Pediatric Neurosurgery. WB Saunders Company, Philadelphia, 1994, pp297-298.