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Head Size - Infants

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The infant's head is enlarging, but the doctor observes that the fontanelles are not bulging, and the infant is intact, neurologically speaking; s/he has no symptoms, i.e., is neither irritable, nor unusually sleepy -- then, follow carefully.


In the Case of Macrocephally, How Is The Diagnosis of Hydrocephalus Typically Made?


"The various types of hydrocephalus can present differently in different age groups."

"Acute hydrocephalus typically presents with headache, gait disturbance, vomiting, and visual changes. In infants, irritability or poor head control can be early signs of hydrocephalus. When the third ventricle dilates, the patient can present with Parinaud syndrome (upgaze palsy with a normal vertical Doll response) or the setting sun sign (Parinaud syndrome with lid retraction and increased tonic downgaze). Occasionally, a focal deficit, such as sixth nerve palsy, can be the presenting sign. Papilledema is often present, although it may lag behind symptomatology. Infants present with bulging fontanelles, dilated scalp veins, and an increasing head circumference. When advanced, hydrocephalus presents with brainstem signs, coma, and hemodynamic instability." 

"What causes hydrocephalus?"

"There are two main types of hydrocephalus: congenital or acquired. The former means that the problem existed at birth, although it may not noticeably manifest itself until later in life, perhaps even adulthood. The latter means that the root cause of the hydrocephalus, whether it is head trauma, tumor or infection, occurred after birth."

"Aqueductal Obstruction, or Stenosis, is the most common cause of congenital hydrocephalus. The cerebral aqueduct, which conducts CSF from the third to the fourth ventricle, is blocked due to defect, inflammation, tumor or hemorrhage. This forces CSF fluid to back up, thereby causing hydrocephalus."

"Arnold-Chiari malformation is the most common cause of congenital communicating hydrocephalus. It is characterized by elongation of the medulla oblongata so that the fourth ventricular foramina open below the level of the foramen magnum. Cerebrospinal fluid passing from these foramina cannot pass upward to the arachnoid granulation for reabsorption because the subarachnoid space is blocked at the level of the foramen magnum by an associated protrusion of the cerebellum into the foramen. Arnold-Chiari malformation is commonly associated with flattening of the base of the skull (platybasia), abnormalities in the cervical vertebrae, spina bifida, meningomyelocele, and syringomyelia."

Note: The treatments for Chiari malformation are based on the occurrence of clinical symptoms rather than the radiological findings.

Thus, "After a patient presents with symptoms typical of Arnold-Chiari malformation and a thorough neurological examination is performed, the malformation is generally confirmed with an imaging study of the brain and cervical spinal cord, most commonly an MRI. The sagittal MRI images are the best for demonstrating the descent of the cerebellar tonsils below the level of the foramen magnum. Special MRI imaging that evaluates the flow of cerebrospinal fluid at the base of the brain may also be used to evaluate the severity of the compression at the foramen magnum."

"What Are Some Common Treatments?"

"If a patient is confirmed to have a significant Type I Arnold-Chiari malformation treatment usually depends on symptoms and the patient's preferences. Asymptomatic patients usually do not require treatment. If symptoms are intolerable, the most common treatment offered by a neurosurgeon is a Chiari decompression (also called a posterior fossa decompression, suboccipital craniectomy or foramen magnum decompression). This treatment aims to open up the foramen magnum to make more room for the descended tonsils. It can be accompanied by enlargement of the dura covering the brain in that area and sometimes resection or shrinking of the descended tonsils. For more information about this procedure see the Chiari decompression page...."

"Type I Arnold-Chiari Malformation; What Is It?" in Nervous System Diseases.  <>

"Because intervention on the Chiari malformation is based more on symptomatology than on structural characteristics, the exact anatomic definition beyond the requirement of tonsillar herniation is not always germane to the specific choice of treatment."

R. Yassari, D. Frim / Pediatr Clin N Am 51 (2004) 477–490 [p.479]   <">In infants with hydrocephalus, CSF builds up in the central nervous system, causing the fontanelle (soft spot) to bulge and the head to be larger than expected. Early symptoms may also include: