Three doctors described this condition in the 1920s and 1930s and their names stayed attached to it, which is why the title is so long. Families usually shorten it to GSS, and so does this page.
What is it?
GSS is one of the inherited prion diseases. Prion protein, which everyone makes, folds into the wrong shape and builds up in the brain. In GSS the damage falls first and hardest on the cerebellum, the part of the brain that coordinates balance and movement.
It is extremely rare, rarer than CJD. Prion diseases lists the other conditions in the group, and the history of prion disease covers where the names came from.
What causes it?
A change in PRNP, the gene carrying the instructions for prion protein. Several different changes can cause GSS, and the two most common are written P102L and A117V.
It is inherited in an autosomal dominant pattern. One changed copy is enough, and someone who carries it has a 50 percent chance of passing it to each child. A genetic counsellor is the person to talk to about what this means in a particular family, and that conversation comes before any test. Choosing not to be tested is a valid choice. Genetic counselling comes first explains the usual steps.
How does it usually begin?
Unsteadiness is the typical first sign: changes in walking, loss of balance and poor coordination, which doctors call ataxia. Some people have symptoms resembling Parkinson’s disease at the start.
Later, speech can become difficult, and other symptoms may include unusual eye movements, hearing and vision problems including double vision, stiffness in the limbs, weak legs, reduced reflexes, tingling sensations and dementia. Memory and thinking are usually affected later than in CJD rather than first.
Symptoms generally start in midlife, in the 30s, 40s or 50s, and reviews note that onset can occasionally be as early as the 20s. The CJD Foundation gives a duration of 2 to 10 years, and published reviews give a mean of about 5 years. How long it runs depends partly on which gene change it is, and no one can predict it for an individual.
How is it diagnosed?
Through a clinical examination, the family history, a brain MRI, spinal fluid testing and a gene test, which is what confirms it.
Some tests behave differently in GSS than in sporadic CJD. The EEG pattern and the spinal fluid marker 14-3-3 used in CJD are usually not found here, and the spinal fluid seeding test known as RT-QuIC can be negative depending on which gene change is involved and which version of the test the laboratory runs. A negative result on one test does not rule GSS out. How prion disease is diagnosed goes through the tests.
What care and treatment are there?
No treatment stops the disease. Because GSS often runs over years, a good deal of the care is about living with changing balance, speech and movement: physiotherapy, speech and language therapy, equipment at home and help with falls. Symptoms such as stiffness, poor sleep, pain and low mood can be treated.
A palliative care team can be asked in early, long before the last stage, and many families find that helps. What to expect covers the practical side, and support groups lists people who can talk with you.
Research on the inherited forms is active, and current trials keeps the list with eligibility as the sponsors state it.
Where next?
GSS: more detail is the clinical version of this page, and GSS for researchers the scientific one. Genetic prion disease covers the inherited forms together.
Nothing here describes a particular person. Questions about symptoms, test results or what a gene change means in your family belong with a neurologist and a genetic counsellor.