The first high incidence rate of the disease occurred during World War II when ALS in Guam was more prevalent than elsewhere in the world.
This article discusses the symptoms, timelines, possible causes, and prognosis associated with the disease.
Guamanian ALS Symptoms
Guamanian ALS, or ALS/PDC, presents with symptoms of all three disorders, which can include:
Muscle twitches in the arms, legs, shoulders, or tongue Muscle weakness, cramps, stiffness, and tightness Slurred or muffled speech Difficulty chewing, swallowing, talking, or forming sentences Immobility as the disease worsens Difficulty breathing Memory changes Difficulty concentrating Impaired sense of judgment Difficulties with interpreting visual information Visual hallucinations Paranoia and delusions Mood changes, such as depression, anxiety, and irritability Sleep changes that include rapid eye movement sleep disorder or excessive daytime drowsiness
Causes
The cause of ALS/PDC is hard to determine because of the lack of new cases in the region. However, the study of the disease thus far has come to one theory of its cause: neurotoxicity caused by β-N-methylamino-L-alanine (BMAA), a naturally occurring diamino acid found in cyanobacteria and certain microorganisms.
The amino acid is found in blue-green algae and has been shown to cause motor neuron disease when tested in animal studies. Specific plants used in food and medicine in Guam, known as cycad plants, have high levels of BMAA. Fruit bats are also thought to accumulate high levels of BMAA and pass it on to humans when consumed as food.
Since then, limited and controversial research has suggested that BMAA accumulation and consumption can increase a person’s risk of developing neurodegenerative disorders such as ALS, Alzheimer’s disease, and Parkinson’s disease.
Other research suggests that the flour made from the seeds of the cycad plant that haven’t been adequately detoxified contributed to the onset of ALS/PDC. When the seeds still contain toxins, they act as a poison in the body and lead to neurodegeneration.
Diagnosis
During the Guamanian ALS/PDC endemic, diagnostic processes may have been different than they are now. Currently, medical providers follow what is known as the El Escorial or Airlie House criteria to diagnose ALS. These criteria were not developed until 1991. Because of that, they couldn’t be used during the cluster of cases in the 1940s.
Doctors relied heavily on symptom collection, healthy history, and other diagnostic tools available to them at the time. Cognitive assessments had been around for decades at that point and were likely for judging the level of impairment in people with ALS/PDC. Magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), and other tests for diagnosing ALS and Parkinson’s dementia today were not around during the Guam cluster.
Currently, the tests that can work to diagnose ALS/PDC include:
Neuroimaging tests such as an MRI or angiography (MRA) Single-photon emission computed tomography (SPECT) Cognitive assessments, such as the Mini-Mental State Examination (MMSE), Raven’s Coloured Progressive Matrices (RCPM), the paired-associate learning test (PALT), the Frontal Assessment Battery (FAB) test, and the Standard Language Test of Aphasia (SLTA)
The cognitive tests are designed to test for brain function, psychomotor speed, verbal fluency, short-term memory, and frontal lobe function. The SLTA tests for aphasia, which is a disorder that causes a person to lose their ability to communicate with others.
In some cases, an autopsy can help diagnose the disease.
Treatment
Treatment for Guamanian ALS focuses on managing symptoms. Because it is progressive and there is no cure for it, treatment can only improve a person’s quality of life before they succumb to the disease. During the Guam cluster, medicines were not as readily available as they are today.
Current ALS and PDC treatments, such as cholinesterase inhibitors and levodopa/carbidopa, were not invented until long after the 1940s.
Physical, occupational, and speech therapy were all well established by the time the people of Guam started experiencing high rates of ALS/PDC. However, whether these treatments helped them cope with symptoms is unclear.
Currently, all of the treatments mentioned above can help treat the disease.
Prognosis
ALS/PDC is a fatal disease. When a person is diagnosed, treatment will prolong their life and keep symptoms at bay. Typically, people with the condition can expect to live anywhere from four to six years following their diagnosis.
Summary
Guamanian ALS, often referred to as ALS/PDC, is a neurodegenerative disease that affected much of the population of Guam during and shortly after World War II. People with the disease experienced the typical symptoms of ALS and Parkinson’s dementia. Though the cause of the disease isn’t clear, the leading theory is that people in Guam had consumed a large number of cycad plants.
The plant contained a neurotoxin known as BMAA, leading to the degeneration of neurons and, eventually, disease. Diagnosing ALS/PDC wasn’t easy in the 1940s. In 1956, the National Institute of Neurological Disorders and Stroke opened a research center to help diagnose and treat those afflicted with the disease and understand more about it.
ALS/PDC is fatal, so treatment can only improve quality of life rather than cure it. That said, cases of Guamanian ALS have decreased significantly since the years following the war, and incidence rates have dropped to almost zero in recent years.
A Word From Verywell
The Guamanian ALS cluster that occurred on the island of Guam after World War II may seem like an isolated incident. However, other areas of the world, such as Kii, Japan, have experienced similar endemics.
The disease is now considered incredibly rare, so it’s highly unlikely that you will develop it at any point in your life. Because the amino acid suspected to cause the disease is found in blue algae and the cycad plant, keep yourself and your pets safe by avoiding consumption of those two plants.
