Brain buzz: The Basal ganglia
The basal ganglia (or basal nuclei) is a group of subcortical nuclei, of varied origin, in the brains of vertebrates including humans, which are situated at the base of the forebrain. Basal ganglia are strongly interconnected with the cerebral cortex, thalamus, and brainstem, as well as several other brain areas.
The “basal ganglia” refers to a group of subcortical nuclei responsible primarily for motor control, as well as other roles such as motor learning, executive functions and behaviors, and emotions. Disruption of the basal ganglia network forms the basis for several movement disorders. We have seen an increased amount of calcification in Will’s basal ganglia since his first MRI at nine months old. For more information about functional neuroanatomy you can find it here: Functional Neuroanatomy of the Basal Ganglia.
Spasticity is caused by damage to parts of the brain that send the messages for GABA to be released. The damage may occur anywhere along the pathway, from the brain to the brainstem to the spinal cord. The end result is the same: deficiency of GABA and a relative excess of excitatory impulses. The cause of dystonia is not understood nearly as well as the cause of spasticity. It is thought to be due to damage to the basal ganglia, deep structures in the brain that adjust the amount of movement that occurs when people tell a muscle to move. The cause of athetosis (writhing movements) is probably similar. The dystonias are a group of disorders characterized by excessive involuntary muscle contractions leading to abnormal postures and/or repetitive movements. Chorea (nonrhythmic, jerky, rapid, nonsuppressible involuntary movements) is due to damage to a different region of the basal ganglia, so that output from a structure called the internal globus pallidus is less than normal.
It isn’t clear to me if Will has dystonia or spasticity; he could be experiencing both. We see that his tone inhibits him from being able to tolerate his AFOs and because he can’t use those, isn’t able to stand in his stander. I have not seen athetosis or chorea, but Will’s strong tone inhibits him from being able to weight-bear. We have had pediatric rehab doctors, and neurologists suggest anticholinergic medications, baclofen, and gabapentin. The problem with using these medications on Will is that he has severe central hypotonia. Anticholinergics and medications like gabapentin are sedating; these side effects will worsen Will’s central tone, and he would be at a higher risk for aspirating. Given the risk potential of worsening Will’s central tone, we felt that targeting and treating the overexcited muscles is advantageous. We consulted with a local pediatric neurologist who treats patients with similar symptoms with Botox injections.
Botulinum toxin (BoNT) is a potent neurotoxin produced by Clostridium botulinum that causes regional muscle weakness through its action as a zinc endopeptidase cleaving specific proteins involved in vesicular fusion. Disruption of these fusion proteins interferes with the release of acetylcholine at the neuromuscular junction, resulting in localized muscle weakness. It is also viewed as the treatment of choice for spasmodic dysphonia (i.e., laryngeal dystonia), limb dystonia, and oromandibular dystonia.
Why use Botox for spasticity?
Botox helps relax the muscles by blocking messages from the brain that tell muscles to contract (tighten). Botox injections can help increase mobility, relieve pain, maximize comfort, facilitate muscle growth and ease caregiving. We are hoping that with the use of Botox, he will be able to tolerate his AFO’s and participate in weight-bearing activities.
How are Botox injections done?
The interventional radiologist uses an ultrasound and muscle stimulator to locate the targeted muscles for injection. Once the muscle is located, a tiny needle is used to inject a small amount of Botox into the muscle. This procedure is repeated for each of the desired muscles. Will’s neurologist will not use ultrasound or an interventional radiologist to target his muscles, his muscles are easy to locate and can be done safely without ultrasound.
We look forward to updating you on Will’s Botox treatment!