- Hydrocephalus (HP:0000238): Hydrocephalus is an active distension of the ventricular system of the brain resulting from inadequate passage of CSF from its point of production within the cerebral ventricles to its point of absorption into the systemic circulation. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:2182)
- Coarse facial features (HP:0000280): Absence of fine and sharp appearance of brows, nose, lips, mouth, and chin, usually because of rounded and heavy features or thickened skin with or without thickening of subcutaneous and bony tissues. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:2182)
- Strabismus (HP:0000486): A misalignment of the eyes so that the visual axes deviate from bifoveal fixation. The classification of strabismus may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset and the relevance of any associated refractive error. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:2182)
- Nystagmus (HP:0000639): Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:2182)
- Adducted thumb (HP:0001181): In the resting position, the tip of the thumb is on, or near, the palm, close to the base of the fourth or fifth finger. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:2182)
- Seizure (HP:0001250): A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:2182)
- Spasticity (HP:0001257): A motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes with increased muscle tone, exaggerated (hyperexcitable) tendon reflexes. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:2182)
- Agenesis of corpus callosum (HP:0001274): Absence of the corpus callosum as a result of the failure of the corpus callosum to develop, which can be the result of a failure in any one of the multiple steps of callosal development including cellular proliferation and migration, axonal growth or glial patterning at the midline. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:2182)
- Absent septum pellucidum (HP:0001331): Absence of the septum pellucidum (meaning translucent wall in Latin - SP), also known as the ventricle of Sylvius. The septum pellucidum is a thin, triangular double membrane separating the frontal horns of the right and left lateral ventricles of the brain. It extends between the anterior portion of the corpus callosum, and the body of the fornix and its width varies from 1.5 to 3.0 mm. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:2182)
- Holoprosencephaly (HP:0001360): Holoprosencephaly is a structural anomaly of the brain in which the developing forebrain fails to divide into two separate hemispheres and ventricles. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:2182)
- Joint stiffness (HP:0001387): Joint stiffness is a perceived sensation of tightness in a joint or joints when attempting to move them after a period of inactivity. Joint stiffness typically subsides over time. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:2182)
- Aqueductal stenosis (HP:0002410): Stenosis of the cerebral aqueduct (also known as the mesencephalic duct, aqueductus mesencephali, or aqueduct of Sylvius), which connects the third cerebral ventricle in the diencephalon to the fourth ventricle, which is between the pons and cerebellum. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:2182)
- Increased intracranial pressure (HP:0002516): An increase of the pressure inside the cranium (skull) and thereby in the brain tissue and cerebrospinal fluid. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:2182)
- Hemiplegia/hemiparesis (HP:0004374): Loss of strength in the arm, leg, and sometimes face on one side of the body. Hemiplegia refers to a severe or complete loss of strength, whereas hemiparesis refers to a relatively mild loss of strength. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:2182)
- Severe intellectual disability (HP:0010864): Severe intellectual disability (ID) is defined as a type of ID characterized by severely sub-average adaptive functioning and intellectual functioning, with an intelligence quotient (IQ) the range of 20-34. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:2182)
These phenotypes are associated with the disease Hydrocephalus with stenosis of the aqueduct of Sylvius (ORPHA:2182).