Neurology II Flashcards
What is tegmental (Benedikt’s) Syndrome?
Due to lateral tegmental vascular infarct (in the midbrain)
Damage occurs to:
Red nucleus
Superior Cerebellar peduncle
Medial lemniscus
Spinothalamic tract
Oculomotor Nerve
Clinical deficits:
Cerebellar symptoms in contralateral limbs
(Intention tremor) – Red nuc.& Sup. Cer. peduncle
Contralateral loss of two-point tactile discrimination and loss of pain and thermal sense – Medial lemniscus & Spinothalamic tract
Ispilateral oculomotor nerve palsy – oculomotor nerve
What is superior alternating hemiplegia (Weber’s syndrome)?
Damage to ventral mesencephalon
**Damage occurs to (resulting in):** Corticospinal tract (contralateral hemiplegia)
Corticobulbar tract (contralateral hemiparesis of lower face)
Oculomotor nerve root fibers (Ipsilateral paralysis of oculomotor nerve)
What is Middle alternating hemiplegia?
Damage to the Ventral lower Pons
**Damage to (results in):** Corticospinal tract (contralateral hemiplegia)
Corticobulbar tract (Contralateral hemiparesis of lower face)
Abducens Nerve (Lower motor impairment of ipsilateral lateral rectus –> internal strabismus)
Millard-Gubler Syndrome
Damage to Ventral and Lateral pons
**Damage to (results in):** Corticospinal tract (contralateral hemiplegia)
Corticobulbar tract (contralateral hemiparesis of lower face)
Abducens nerve (lower motor impariment of ipsilateral lateral rectus –> internal strabismus)
Facial nerve (ipsilateral lower motor impairment of entire face)
Inferior alternating hemiplegia
Damage to ventral medulla
**Damage to (results in):** Corticospinal tract (contralateral hemiplegia)
Hypoglossal nerve (Lower motor impairment of ipsilateral tongue)
What are the brainstem CN reflexes?
Corneal reflex (CN V sensory –> CN VII Motor)
Pupillary Light Reflex (CN II sensory –> CN II motor)
Jaw Jerk Reflex (CN V sensory –> CN V motor)
Will basal ganglion lesions result in Upper or lower Motor neuron loss, or both?
Upper Motor Neuron only!
Although the basal ganglion controls amount of movement or how easy it is to make movements, it has no direct connection to lower motor neurons
What is the direct pathway through the basal ganglia?
Cerebral Cortex (all lobes) activate thespiny striatal neurons of the Striatum with Glutamate
Striatum (Caudate+Putamen) inhibits the Medial Palladial Segment (MPS) and Substantia Nigra pars reticularis (SNr) with GABA/Substance P
With MPS and SNr inhibited, they cannot inhibit the Thalamus (VA and VLa)
The Thalamus (VA and VLa) is then able to activate the Supplementary Motor Area (SMA) with Glutamate, thus facilitating movement
What is the indirect pathway of the basal ganglion?
Cerebral Cortex activates the spiny striatal neurons of the striatum with Glutamate
Striatum Inhibits the Lateral Palladial Segment (LPS) with GABA/Encephalin
The inhibited LPS then has decreased GABA release on the Subthalamic Nucleus (STN), thu disinhibiting it
The STN is then able to activate the MPS and SNr with Glutamate
Activated MPS and SNr inhibits the Thalamus (VA/VLa) with GABA
The inhibited Thalamus then has decreased Glutamate release onto the Supplementary Motor Area
And movement is suppressed
What are spiny neurons?
Efferent Neurons of the striatum
- Radiating dendrites w/spines
- Axons project to other Basal Ganglion nuclei
- Produce TWO DIFFERENT neurotransmitter combinations:
GABA/Substance P (Direct pathway)
GABA/Enkephalin (Indirect pathway)
What are aspiny neurons?
Local interneurons of Striatum
- Lack dendritic spines
- DO NOT project outside of striatum
- Produce many different NTs
(cholinergic ones most clinically important)
What are the affects of dopamine on the basal ganglion?
- directly activates spiny striatal neurons of direct pathway (to release GABA/Substance P)
- directly inhibits spiny striatal neurons of indirect pathway (to suppress release of GABA/Enkephalin)
- inhibits cholinergic aspiny striatal neurons that tonically activate spiny neurons of the indirect pathway (further inhibiting said pathway)
How does Parkinson’s disease affect the basal ganglion?
Substantia nigra pars compacta produces less and less dopamine resulting in:
Loss of dopaminergic input to basal ganglion
–> spiny neurons that release GABA/Substance P are less active
–> Spiny neurons that release GABA/Enkephalin are more activate
–> Hypokinetic disorder of parkinson’s:
Bradykinesia
Rigidity
Resting Tremor
Postural/Gait instability
Difficulty initiating movement
What is Huntington’s disease and how does it affect the basal ganglion?
Autosomal dominant hereditary neurodegenerative disease
- progressive degeneration of striatum (GABA/Enk neurons)
–> Loss of GABA/Enk neurons results in a decrease in indirect pathway activity, leading to a hyperkinetic disorder
Symptoms:
Chorea
Hypotonia
Psychiatric symptoms (depression, irritability, anxiety)
Cognitive decline
What is Hemiballism and what causes it?
Involuntary flinging of extremeties on contralateral side of the lesion
Results from a lesion (usually due to stroke) in the Subthalamic nucleus
Without the Subthalamic nucleus, the indirect pathway of the basal ganglion is unable to suppress unwanted movement through activation of the medial palladial segment and SNr (which would release GABA and inhibit the Thalamus)
–> without this pathway, the thalamus is constantly activated
