These issues can vary depending on the symptoms that manifest in a specific individual and the severity of those symptoms, which is ultimately determined based on where the individual is situated on the L1 syndrome spectrum.Spasticity is one of the most common signs of L1 syndrome and is seen in all four major clinical phenotypes. It is characterized as the continuous contraction of certain muscles, leading to muscle stiffness which can interfere with normal movement and speech. In three of the major phenotypes (except HSAS), this spasticity is presented as spastic paraplegia, where the muscles of the lower limbs are stiff and continuously contracted. This spastic paraplegia often manifests itself as a gait (walking motion) disorder, specifically shuffling gait in MASA syndrome patients, which acts as a source of impairment and stress due to postural instability, and leads to poor quality of life and increased mortality.Aphasia is also a common disorder, especially in people with MASA syndrome (a disorder on the L1 syndrome spectrum) and describes a range of language impairments with respect to syntax (structure), semantics (meaning), phonology (sound), morphology (structure), and/or pragmatics in language comprehension or expression. People with aphasia, as well as their family members, often experience a poor quality of life due to the social isolation and depression caused by this language impairment and therefore may seek therapy to enable functional and socially relevant communication.
After birth, in the presence of suggestive features (such as macrocephaly), hydrocephalus can be confirmed with noninvasive imaging including head magnetic resonance imaging, computed tomography, or ultrasound showing ventriculomegaly, or direct measurement of intracranial pressure through invasive techniques such as lumbar puncture. Further, the spasticity found in patients with HSAS can be easily demonstrated by examining the deep tendon reflexes and the extensor plantar reflex (which will both be abnormally brisk and strong due to damage to the cortex and internal capsule of the brain). There are various types of genetic testing that can be used to confirm an L1 syndrome diagnosis in a patient. After birth, genetic tests carry a low-risk of physical complications and are minimally-painful: for the patient, the process requires a small amount of blood being drawn from the arm using a needle. However, prenatal genetic testing carries significant risks for both the fetus and mother due to the need to remove genetic material from the fetus while it is still in utero. In order to conduct prenatal genetic testing, the mother and fetus must undergo either amniocentesis (the surgical puncturing of the amniotic sac, which holds the fetus in the womb) or, less frequently, chorionic villus sampling.