What are the other Names for this Condition? (Also known as/Synonyms)

• EHS (Eight-and-a-Half Syndrome)

What is Eight-and-a-Half Syndrome? (Definition/Background Information)

• Eight-and-a-Half Syndrome (EHS) is a rare neural condition involving lesions at various locations in the brain, resulting in a set of associated symptoms. A lesion may be described as a wounded region in an organ or tissue
• The specific locations are the cranial nerve VI (abducens) nucleus, a portion of cranial nerve VII (facial nerve) consisting of a bundle of structures, and the medial longitudinal fasciculus (MLF), a fiber tract in the brainstem
• The cranial nerves are 12 pairs of nerves in the back of the brain that send signals to the rest of the body. Lesions in these regions lead to a combination of three conditions:
  • Horizontal Gaze Palsy: This is a visual condition in which the patient is unable to move his/her eyes sideways (side-to-side)
  • Facial Nerve Palsy: This condition results in facial paralysis
  • Internuclear Ophthalmoplegia (INO): In this condition, there is an absence of coordination between the eyes such that when looking to a side, one eye does not turn fully
• A lesion involving cranial nerve VI, the MLF, and a connected unit known as the paramedian pontine reticular formation (PPRF), is known as one-and-a-half syndrome. Additionally, lesions in cranial nerve VII leads to the condition known as Eight-and-a-Half Syndrome. The name comes from adding one-and-a-half (1.5) to the number in cranial nerve VII (7)
• Eight-and-a-Half Syndrome can develop from many causes. It is most often due to vascular (related to blood vessels) lesions or demyelinating (damage to the protective fibers on nerve cells) lesions. Other causes include congenital (existing from birth) conditions and abnormal growth of tissue
• The signs and symptoms of Eight-and-a-Half Syndrome include facial weakness and droopiness, both eyes not moving together, and limited eye movement. EHS is diagnosed clinically. An MRI scan may be ordered to determine the cause of the condition. It may help in detecting lesions (small and big) or elucidate on other possible causes
• The treatment of Eight-and-a-Half Syndrome depends on each individual case. Some may opt to treat symptoms of EHS and its resulting effects, while surgery may be required in some cases. The type of surgery performed depends on factors related to the lesion such as its location, size, and overall severity of the condition
• The prognosis of Eight-and-a-Half Syndrome varies from one individual to another. However, early diagnosis and adequate treatment can lead to better outcomes