The simplest way to assess intellectual abilities is through language skills. Language function is receptive (understanding speech or gestures) and expressive (speech and use of gestures). Abnormalities of language resulting from cerebral hemisphere disorders are referred to as aphasias. Anterior, expressive, or Broca aphasia is characterized by sparse, non-fluent language. Posterior, receptive, or Wernicke aphasia is characterized by an inability to understand language, with speech that is fluent but nonsensical. Global aphasia refers to impaired expressive and receptive language.
The cranial nerve evaluation assesses brainstem integrity but depends on the stage of brain maturation and the ability to cooperate. A colorful toy may capture a young child’s attention and permit observation of coordination, movement, and cranial nerve function.
Smell can be assessed in verbal, cooperative children older than2 years of age. Aromatic substances (perfumes, vanilla) shouldbe used instead of volatile substances (ammonia), which irritate the nasal mucosa and stimulate the trigeminal nerve.
Full-term newborns in a quiet awake state follow human faces,lights in a dark room, or large, opticokinetic strips. Visual acuity has been estimated to be 20/200 in newborns and 20/20 in6-month-old infants. Standard visual charts displaying picturesinstead of letters can be used to assess visual acuity in toddlers.Peripheral vision is tested by surreptitiously bringing objectsinto the visual field from behind. A reduced pupillary reactionto light suggests anterior visual pathway lesions, including theretina, optic nerves, and chiasm. Unilateral optic nerve lesionsare identified by the swinging flashlight test. With an optic nerveabnormality, both pupils constrict when light is directed into thenormal eye. When light is swung over to the abnormal eye, bothpupils dilate inappropriately; this is called an afferent pupillary defect or Marcus Gunn pupil. Interruption of the sympatheticinnervation to the pupil produces Horner’s syndrome (ptosis,miosis, and unilateral facial anhidrosis). In this instance, anisocoria (unequal pupils) is more pronounced in a dark room,because the affected pupil is unable to dilate appropriately.Lesions of the posterior visual pathway, including the lateralgeniculate, optic radiations, and occipital cortex, have normalpupillary light reactions but are expressed by loss of visual fields.
Cranial Nerves III, IV, and VI
These three cranial nerves control eye movement and are most easily examined with the use of a colorful toy to capture the child’s attention. For infants too young to fix and follow, rotating the infant’s head assesses oculocephalic vestibular reflexes (doll’s eye maneuver). If the brainstem is intact, rotating a newborn or comatose patient’s head to the right causes the eyes to move to the left, and vice versa. In awake, older patients, voluntary eye movements mask the reflex.
Abnormalities of these cranial nerves may cause diplopia (double vision). With unilateral third cranial nerve (oculomotor nerve) palsy, the involved eye deviates down and out (infraducted, abducted), with associated ptosis and a dilated, mydriatic pupil. Injury to cranial nerve IV (trochlear nerve) causes weakness of downward eye movement with consequent vertical diplopia. Cranial nerve VI (abducens nerve) palsy results in the inability to move the eye outward. Because cranial nerve VI has a long intracranial route within the sub-arachnoid space, failure of abduction of one or both eyes is a frequent, but nonspecific, sign of increased ICP.