Symptoms and Associated Conditions of Hydranencephaly

At birth, a baby with hydranencephaly may appear surprisingly “typical.” This is because the brainstem, which is often preserved, controls the basic survival skills of a newborn ^[1][2]. However, as the baby grows, the absence of the cerebral cortex (the part of the brain responsible for higher processing) leads to specific physical and neurological challenges.

Physical Signs and Reflexes

Because the brainstem and cerebellum are usually intact, many infants with hydranencephaly display primitive reflexes—automatic movements like sucking, rooting for a bottle, and grasping a finger—that are normal for any newborn ^[1][3].

However, even if your baby appears to suck well, neurological impairments can cause unsafe swallowing, leading to aspiration (milk going into the lungs) ^[1]. It is highly recommended to ask for a swallow study or an evaluation by a feeding specialist early on to ensure safe feeding.

The most common physical sign noticed at or shortly after birth is macrocephaly (an enlarged head size) ^[1][4]. This happens because the fluid filling the skull can create pressure, causing the head to grow faster than expected ^[5]. Doctors often track head circumference closely to determine if a shunt (a tube to drain excess fluid) is needed to relieve pressure and ensure the baby’s comfort ^[2][6].

Neurological Symptoms

As the infant develops, the lack of cerebral tissue becomes more apparent through several neurological symptoms:

• Seizures: Many children with hydranencephaly develop epilepsy ^[4][2]. These may look like sudden stiffening, rhythmic twitching, or “blank” staring spells. Work with your pediatric neurologist to create a seizure action plan. This will tell you exactly what to do during a seizure, when to give emergency medication, and when it is necessary to call 911 or visit the emergency room.
• Spasticity and Hypertonia: This involves increased muscle stiffness or “tone,” making it difficult for the baby to move their limbs smoothly ^[1][3].
• Developmental Delays: Significant delays in reaching milestones like sitting up, rolling over, or speaking are expected due to the missing cerebral hemispheres ^[3][2].
• Sensory Impairments: Vision is frequently affected; while the eyes themselves may be healthy, the brain may not be able to process what they see. Some babies may also have optic nerve atrophy (wasting of the nerve that carries signals to the brain) ^[7]. Hearing may also be impaired, though the degree varies ^[8][1].

“Hidden” Endocrine Conditions

The hypothalamus and pituitary gland, located at the base of the brain, are responsible for regulating the body’s hormones. If these areas are affected, it can lead to “hidden” conditions that aren’t visible to the eye but are critical to manage ^[4][9]. About 22% of infants with hydranencephaly experience at least one endocrine complication ^[4].

Central Diabetes Insipidus (AVP-D)

This is not related to blood sugar (diabetes mellitus). Instead, it is a condition where the body cannot balance its water levels because it lacks antidiuretic hormone (ADH) ^[4][10].

• Signs in Infants: Look for polyuria (excessive amounts of very pale urine/heavy diapers) and polydipsia (extreme thirst or dehydration) ^[10][11]. Because healthy newborns naturally have frequent wet diapers, diagnosing DI requires looking for additional signs like rapid weight loss, severe dehydration, or extreme irritability. Doctors will also monitor your baby’s blood sodium levels to confirm the diagnosis ^[10].
• Management: This is often treated with a medication called desmopressin, which replaces the missing hormone ^[10][4].

Other Hormone Issues

• Hypothyroidism: The body may not produce enough thyroid hormone, which is necessary for growth and metabolism ^[4][9].
• Hypocortisolemia: A deficiency in cortisol, the “stress hormone,” which helps the body respond to illness or injury ^[4].
• Temperature Dysregulation: Because the hypothalamus acts as the body’s thermostat, babies may have trouble staying warm or may develop unexplained fevers even when they aren’t sick ^[4][12].

Monitoring these hidden symptoms is a vital part of providing a comfortable and stable environment for your baby ^[3][4].