Initial presentation to a pediatrician or pediatric neurologist depends on the etiology of the underlying condition leading to macrocephaly. In many cases, an increased HC may be first the presenting sign of the underlying condition. Therefore, it is important to track postnatal HC and HC throughout the child’s early development [2]. When evaluating premature infants, age should be adjusted for the degree of prematurity. Many computer-based electronic records now perform this adjustment automatically, but it is crucial to check that this has been compensated for; a 4–6-week error in age may significantly skew the HC chart of a neonate. Any significant increase or decrease in HC between percentiles should be a cause for further evaluation. A HC percentile that is markedly different from the length and weight percentiles should also be considered carefully. When evaluating a child’s HC, it is also important to note the HC of both parents because benign enlargement of the subarachnoid space runs in families [6, 21]. Though work-up may still be indicated to confirm such a diagnosis, a child with a large head whose parents have large heads is certainly less concerning than a child with a large head whose parents have small- to mid-sized heads.

Signs and symptoms associated with hydrocephalus may include full anterior fontanels, prominent scalp veins, failure to thrive, decreased appetite, failure to achieve developmental milestones, irritability, or loss of interest due to increased pressure on the frontal lobe [9]. In more severe cases, patients may have papilledema, impaired upward gaze due to compression of the midbrain including Parinaud syndrome, seizures, altered mental status, or even loss of consciousness. In late stages, Cushing’s reflex—the triad of widened pulse pressure, irregular breathing and bradycardia due to increased ICP—and spasticity from stretching of motor fibers over dilated ventricles, may be present [22]. A patient’s presentation depends on the age of onset (corresponding to the degree of suture fusion) and the duration and rate of development of elevated ICP. Children who develop hydrocephalus when they are younger than 2 years of age usually present with macrocephaly while children who develop hydrocephalus when they are older typically present with signs of increased ICP [9, 22].

Conditions associated with megalencephaly are broadly associated with seizures, developmental delay and/or mental retardation. Depending on the etiology of megalencephaly, macrocephaly may be present at birth or develop during early childhood [5]. Some children may show stigmata of the underlying disease. For example, those with neurofibromatosis typically have café au lait spots and axillary freckling while those with Sotos syndrome would present with characteristic features such as a high-prominent forehead and down-slanting palpebral fissures [4, 6].

Mass lesions typically present with signs of increased ICP including altered mental status. The presentation would include macrocephaly only if the lesion or resulting hydrocephalus is left untreated. As the name implies, infants with macrocephaly from benign enlargement of subarachnoid spaces are typically asymptomatic apart from the increased HC. Occasionally they may present with subdural hematoma caused by the larger head size and increased tautness of bridging vessels in the extra-axial fluid spaces [23]. In rare cases, they may present with transient language or motor deficits [21, 24].

Initial evaluation for any child should include a medical history and family history, HC measurements, and a complete physical exam, including neurologic and developmental exams. Hydrocephalus and/or macrocephaly should be suspected in infants with HC crossing percentiles. Imaging studies can determine the presence or absence of megalencephaly, bone proliferative conditions, hemorrhage, or hydrocephalus [25]. Additionally, imaging studies can help identify the cause of hydrocephalus, including aqueductal stenosis and mass lesions.

Infants, including premature infants being screened for IVH, are evaluated by ultrasound. Screening is typically first done 5 days after birth and repeated several weeks later [25]. Computed tomography (CT) or preferably magnetic resonance imaging (MRI) may be used in the evaluation of older children. CT studies have the advantage of requiring no sedation but expose the child to radiation [26] and have poorer resolution. In contrast, MRI studies have better resolution and do not expose the child to radiation, but they typically require sedation.

A widely used alternative to CT is “quick-brain MRI” to assess for hydrocephalus and/or shunt function. Unlike MRI, the single-shot fast-spin echo (SSFSE ) MRI or quick-brain MRI requires no sedation due to the short amount of time required for this imaging. Images acquired through this protocol allow assessment of abnormal fluid collections, ventriculomegaly, and shunt positioning [27, 28], sparing children unnecessary exposure to radiation. However, short MRI sequences can produce movement artifacts that can be mistaken for intraventricular hemorrhage [29]. A full discussion of how to image children may be found in Chap. 20.

If infectious causes are suspected, and there is no evidence of hydrocephalus or mass lesion on imaging, a lumbar puncture should be performed. Additional genetic testing or metabolic testing may be indicated to diagnose specific megalencephalic conditions.

The underlying cause of macrocephaly will dictate the treatment plan. If abnormal bone proliferation or megalencephaly is noted on initial evaluation and imaging studies, appropriate referrals to specialists including pediatric neurologists and geneticists should be made. For many of the megalencephalic conditions, no specific treatment exists. However, specialist management may be required to manage underlying metabolic and/or seizure disorders.

Pediatric neurosurgery should be consulted if hydrocephalus, hemorrhage, and/or a mass lesion are diagnosed. Mass lesions may be resected or biopsied, and depending on the pathologic diagnosis may require additional chemotherapy or radiation therapy. Intracranial bleeds or hematomas may be monitored for resolution with close radiographic follow-up or evacuated depending on the severity of the bleed and symptoms.

As illustrated in Fig. 14.2, the lateral ventricles communicate with the third ventricle through the foramen of Monro while the third ventricle communicates with the fourth ventricle through the aqueduct of Sylvius . Any intraventricular obstruction or obstruction at the level of the foramen or the aqueduct may result in hydrocephalus. In the treatment of hydrocephalus, the primary objective is to drain excess CSF, relieve increased intracranial pressure, and prevent further neurological deterioration. In many cases, hydrocephalus resulting from mass lesions may be cured by resection of the lesion without the need to treat the resulting hydrocephalus. However, hydrocephalus resulting from other etiologies and those with a tumor who are inappropriate candidates for resection or do not resolve their hydrocephalus after tumor resection typically require treatment of hydrocephalus rather than the underlying cause [30].

Despite considerable advancements in hydrocephalus management, a main treatment remains cerebrospinal fluid shunting. The most frequently used type of shunt is the ventriculoperitoneal (VP) shunt . As illustrated in Fig. 14.3, a catheter is inserted into the lateral ventricle and connected to a one-way valve just outside the skull. This valve is then connected to a second catheter that is tunneled subcutaneously into the abdomen and placed into the peritoneal space. The body reabsorbs this fluid through the peritoneal lining. The one-way valve ensures both the direction and rate of CSF flow. Valves may be programmable (i.e., adjustable to different pressures) or non-programmable (set at a predetermined pressure).