Semester 2 Quiz 4

List the 4 deep cerebellar nuclei

1. Dentate 2. Emboliform 3. Globose 4. Fastigial

What are the two types of afferents that synapse on Purkinje Cells?

1. Mossy fibers --> afferents from the spinal cord, pontine nuclei and vestibular system; synapse indirectly to Purkinje Cells via parallel fibers; there are millions of mossy fibers in contact with each purkinje cell 2. Climbing fibers --> afferents from the inferior olivary nucleus (convey info about movement errors to the cerbellum); synapse directly with Purkinje Cells; there is only one climbing fiber in contact with each purkinje cell meaning that info from climbing fibers is very important; each climbing fiber synapses with a given purkinje cell ~50-100x which amplifies the signal

List the functions of the basal ganglia

1. Movement initiation (basal ganglia fires prior to movement) 2. Sequencing movement (basal ganglia fires at the end of movements to switch from one autonomic pattern to the next) 3. Regulating muscle tone 4. Regulating muscle force 5. Involved in working memory and procedural memory 6. Sustained attention 7. Ability to change behavior as task requirements change 8. Motivation

List other, non-motor signs associated with PD

1. Olfactory loss (loss of smell) 2. Depression 3. Hallucinations 4. Pain 5. Orthostatic Hypotension 6. Visual problems 7. GI dysfunction 8. Sleep disorders These may occur prior to motor sx. Often times, pts are not aware of their deficits and therefore need external cuing.

List the 4 cardinal signs of Parkinsons

1. Tremor --> typically an intentional tremor; affects most of PD pts 2. Bradykinesia --> slowness of movements; affects all PD pts 3. Rigidity --> will eventually impact all PD pts 4. Postural instability --> the most disabiling sx of PD because meds do not treat this well and it reduces ability to be independent

Define cerebellar ataxia

A cerebellar sign involving lack of coordination of voluntary movements characterized by wide gait, unsteadiness, and inability to perform tandem gait. Pts will still have normal strength with no hypertonicity or spasticity.

Describe the basal ganglia

A group of subcortical gray matter areas that help to regulate movement. Composed of the caudate, putament, and globus pallidus in the cerebrum, and the subthalamic nucleus and substantia nigra in the midbrain.

Describe the Vestibulocerebellum

AKA the Flocculonodular Lobe. Receives vestibular info in regards to head and body position. Receives info directly from the vestibular system in the inner ear, vestibular nuclei in the brainstem, primary visual cortex, and superior colluculi. Function: helps to coordinate eye movements with body movements, and influences postural muscles.

Caudate + Putamen = ?

Caudate + Putamen = Striatum

Define dysarthria

Cerebellar sign: Difficulty with the motor component of speech (difficulty coordinating muscles of speech)

Define dysmetria

Cerebellar sign: Inability to accurately move an intended distance

Define disdiadochokinesia

Cerebellar sign: Inability to rapidly alternate movements (inability to quickly turn on/off opposing muscle groups)

Define the rebound phenomenon

Cerebellar sign: Inability to turn off the working muscle group so when tested, their arm will come back and they will hit themselves in the face

Define intention tremor

Cerebellar sign: Shaking of the limbs during voluntary movements.

Describe the cerebellar vermis

Connects the two cerebellar hemispheres. Vermis + paravermal region = spinocerebellum

Describe dementia seen with PD and how it differs from dementia in Alzheimers

Dementia in PD: often results in difficulty planning, making decisions, and maintaining goal orientation Dementia in Alzheimers: primarily affects memory

What other S + S might you see in a pt with PD?

Dysarthria --> difficulty with the motor component of speaking Dysphagia --> difficulty swallowing Micrographia --> small handwriting due to bradykinesia

Describe Deep Brain Stimulation (DBS) as a tx for PD

Electrodes are implanted into the subthalamic nucleus or the thalamus. High frequency firing of the electrodes alters the firing pattern of the neurons in the basal ganglia. Can improve tremor, rigidity, and speed of movements. May allow pt to decrease L-DOPA dosages. It is not a cure. Bilateral procedures may be needed for walking and balance problems. Does not make sx totally go away. There are programming visits many times during the first 6 months, and then visits every 6 months thereafter.

Describe how candidates for DBS are determined

FLASQ-PD scoring. 1. Pt needs to have idiopathic PD 2. Pt cannot have any red flags (wide based gait, greater than mild dementia, no autonomic dysfunction) 3. Age (best pts are below 60 y/o, will not do the surgery if pt is above 80 y/o) 4. Amount of improvement in function via L-DOPA (If L-DOPA does not work, DBS will not work either) 5. Will not use if meds are wearing off between doses

Describe the Cerebrocerebellum

Formed by the anterior and posterior cerebellar lobes on the lateral sides of the cerebellum. Function: helps to control distal limb movement and plays a role in motor planning. Input comes from the cerebral cortex via the middle cerebellar peduncle. Purkinje cells in the cerebrocerebellar system project to the dentate nucleus, which is involved in motor planning, and the timing and coordination of movements.

What are the different kinds of nystagmus associated with cerebellar issues?

Gaze evoked nystagmus = only one eye will beat at a time Gaze evoked rebound nystagmus = pt may overshoot their eyes and have to use a corrective saccade

Globus Pallidus + Putamen = ?

Globus Pallidus + Putament = Lentiform Nucleus

What are the two parts of the Globus Pallidus?

Globus Pallidus externus (closer to the putamen) and Globus Pallidus internus (closer to the thalamus).

Describe the pathway of Spinocerebellar output

Info comes in through the spinal cord --> goes through inferior cerebellar peduncle to the cerebellum --> synapses with a purkinje cell in the spinocerebellum --> goes to either the fastigial, globose, or emboliform nuclei --> leaves the cerebellum via the superior cerebellar peduncle --> will then either go out to the vestibular nucleus, or up through the thalamus and on to the cortex --> info then goes back down through the internal capsule and down to the corticospinal tract

Describe the pathway of Vestibulocerebellar Output

Info goes in to the brainstem and either synapses directly with a vestibular nucleus, or goes into the cerebellum via the inferior cerebellar peduncle --> synapses with a purkinje cell --> does not synapse with any deep cerebellar nuclei --> leaves the cerebellum via the superior cerebellar peduncle --> info goes back down to synapse with the vestibular nucleus --> info then goes down via the medial and lateral vestibulospinal tracts

Describe the pathway of Cerebrocerebellar Output

Info starts in the cortex --> goes down and synapses in the ipsilateral pontine nucleus --> goes to the contralateral cerebrocerebellum to synapse with a purkinje cell --> info then synapses with the dentate nucleus --> this info (now efferent) goes up and crosses back over to the ipslateral thalamus and back up to the cortex --> info then goes back down through the internal capsule and down to the corticospinal tract

Describe the tremors seen with PD

Involve both the basal ganglia, and a circuit involving the cerebellum, thalamus, and motor cortex. The rate of tremor development and overall severity of the tremor do not correlate with other motor sx. Tremor responds less well to L-DOPA than rigidity and bradykinesia.

What side of the body is affected by a lesion to the cerebellum?

Lesions to the cerebellum will always impact the ipsilateral side of the body. However, since the vestibulocerebellar pathway goes to the vestibulospinal tract (the medial vestibulospinal tract is bilateral), you may see bilateral deficits

What is the gold standard pharmacological tx for PD?

Levadopa (L-DOPA). Is more effective in treating bradykinesia than postural instability. May or may not help with tremors (dependent on pt)

List all the functions that the cerebellum is responsible for

More than just controlling balance. Has rolls in integrating sensory info from the body with info about intended movements from the cortex. Plays a role in motor planning. Plays a role in the improvement of motor performance through the establishment of autonomic motor skills, involved in procedural memory in regards to motions related to skills. Also plays a role in motor recovery after injury due to its role in motor learning.

Describe the pharmacological tx for PD

PD is due to a loss of DA, but you cannot simply give the pt more DA as it cannot pass the BBB. Because of this, we give L-DOPA which is able to pass the BBB and once inside, it is decarboxylated to form DA. The neurons that decarboxylate L-DOPA into DA are located at the nerve terminals that are already responsible for releasing DA. Carbidopa is usually given simultaneously as it works to inhibit the conversion of DA in the PNS. Even though these meds help to maintain function, PD involves progressive death of neurons and therefore is a progressive and terminal disease. The efficacy of L-DOPA decreases over time (as more neurons die). Significant dyskinesias (excessive movements) may develop over time as a side effect of taking L-DOPA.

What causes PD?

Primarily caused by the death of dopamine producing cells in the substantia nigra, along with death of ACh producing cells in the pedunculopontine nucleus.

Describe sensory ataxia vs. cerebellar ataxia and how to rule out sensory ataxia

Sensory ataxia = ataxia as a result of impaired somatosensory input or peripheral neuropathy. Pt with sensory ataxia will have a + Romberg test (will lose their balance once their eyes are closed as now they are only relying on one system to maintain balance and you need at least 2/3 systems working to remain upright). Pt with cerebellar ataxia will already demonstrate balance issues just trying to stand still.

What are the two parts of the Substantia Nigra?

Substantia Nigra reticulata and the Substantia Nigra compacta.

Describe the 3 cerebellar peduncles

Superior --> efferent fibers (taking info away from the cerebellum) Middle --> cortical afferent fibers (info coming into the cerebellum from the cortex); is the biggest of the three peduncles Inferior --> sensory afferent fibers (info coming into the cerebellum from the spinal region)

Describe how the basal ganglia works

The basal ganglia has no direct connections to UMNs or LMNs, so its influence on motor function occurs through input onto the part of the thalamus that handles motor info, the pedunculopontine nucleus, and the midbrain locomotor region. Direct pathway = activates motor patterns Indirect pathway = smooths movements

What is the Nucleus Accumbens?

The nucleus accumbens is at the anterior pole of where the cuadate and putamen meet. It is important for pleasure/reward pathways.

Describe the structural anatomy of the cerebellum

The outer layer is gray matter, with white matter tracts and cerebellar nuclei within. Is composed of 3 lobes: anterior, posterior, and flocculonodular. Is connected to the brainstem via the superior, middle and inferior cerebellar peduncles.

Describe what is seen as an effect of low dopamine (such as with PD)

There is less faciitation of the direct pathway, making it harder to initiate movements. There is less inhibition of the indirect pathway (which is inhibitory) so there is excessive inhibition of movements. There is also more inhibition of pathways that inhibit the reticulospinal and vestibulospinal tracts. Because of this, the postural muscles are not inhibited (are more active) which leads to rigid movements. The loss of ACh from the pedunculopontine nucleus also contributes to this. The loss of DA results in pts who are more dependent on sensory feedback for movement and less capable of using motor programs that might give greater speed and accuracy of movements.

Describe Purkinje Cells

They control the output to the cerebellar cortex. They inhibit neurons deep in the cerebellar nuclei. They have tons of synapses so there is a ton of info coming into a purkinje cell that is distilled down to one output.

True or False? Purkinje Cells are inhibitory.

True. Purkinje Cells release GABA onto deep cerebellar nuclei neurons. This inhibitory output is regulated by the summation of input from mossy fibers and climbing fibers. All climbing fibers are excitatory and the connection between mossy fibers and parallel fibers can be either inhibitory or excitatory.

Describe the Spinocerebellum

Vermis + Paravermal region = Spinocerebellum. Function: controlling ongoing movements and correction of movements. The spinocerebellum projects to the fasitgial, globose, and emboliform nuclei. All 3 nuclei adjust motor actions through synapses with the brainstem vestibular nuclei and the cerebral cortex.

Describe Chiari Malformation

When there is a decreased size of the skill in the cerebellar region, and the cerebellar tonsils are pushed down through the foramen magnum. Is usually not dx until adolescence or adulthood. S + S: affects all of the cerebellar functions, DCML may be affected, possible vision deficits if the superior/inferior colluculi are affected, compression on the vertebral column can cause pain, anything in the brainstem could be affected (CNs). Tx: surgery.