Right 6th Nerve Palsy
← Looking
Unable to abduct right eye, Larger angle of squint, Double Vision Further Apart
Looking Forward
Right eye turns medially
Looking →
Able to adduct right eye, No obvious squint
Dorsal longitudinal (dorsolateral) fasciculus
fibers from the hypothalamus to the autonomic nuclei and reticular formation of the brainstem’s central gray matter
influence activities such as chewing, swallowing, and shivering.
Lateral lemniscus
Carrying second-order fibers arising from the cochlear nucleus that ascend to the inferior colliculus.
auditory pathway
Medial lemniscus
Connects the second-order neurons of nucleus gracilis and cuneatus (dorsal columns) to the ventral posterior lateral nucleus of the thalamus.
Medial longitudinal fasciculus
carries projections from the superior colliculus to the oculomotor, trochlear, and abducens nuclei
contributes to reflex movements of the eyes in response to visual, auditory, and somatic stimuli.
Cortical vein thrombosis
CVT → propagation to SVT
no association to trauma
Risk factors:
* dehydration → hypercoagulation
Dx: CTA/CTV
Tx: anticoagulation w/ Clexane
VPS reservoir flushing test
Metabolism
- Brain’s small size, ~2% of total body mass, weighs ~1.4 kg.
- Brain’s high metabolic activity: 20% basal O2 consumption, 25% basal glucose consumption.
- Reliable, responsive cerebral blood flow (CBF) required due to ↑ metabolic activity.
- Brain receives 15% of cardiac output at rest (750 ml/min in adults).
- Average CBF: ~50 ml/100 g/min.
- Mean CBF values: white matter 20-30 ml/100 g/min, gray matter 75-80 ml/100 g/min.
- Regional CBF parallels metabolic activity, varies b/w 10 and 300 ml/100 g/min.
- Transmission of electrical impulses in brain by energy-dependent neuronal membrane ionic gradients.
- ↑ in local neuronal activity → ↑ in regional cerebral metabolic rate.
- CBF Δ parallel metabolic Δ (flow-metabolism coupling).
- During functional activation, ↑ in regional CBF tracks cerebral metabolic rate of glucose utilization, may exceed that required for cerebral metabolic rate of O2 consumption (CMRO2).
- Regulatory Δ involved in flow-metabolism coupling have short latency (~1 s), may be mediated by regional metabolic or neurogenic pathways.
- In health, flow and metabolism closely matched, little Δ in oxygen extraction fraction (OEF) across the brain despite wide regional Δ in CBF and CMRO2.
Neurocritical Care
| Feature | SIADH | Cerebral Salt Wasting | Diabetes Insipidus |
|---|---|---|---|
| Serum Sodium | <135 mEq/L | <135 mEq/L | Variable, may be elevated |
| Plasma Osmolarity | <280 mOsmol/L | <280 mOsmol/L | Variable, may be elevated |
| Urine Sodium | >20 mEq/L | >20 mEq/L | Variable |
| Urine Osmolarity | >Plasma Osmolarity | >Plasma Osmolarity | 50-150 mOsmol/L |
| Serum Potassium | Decreased or normal | Increased or normal | Normal |
| Blood Volume | Increased | Decreased | Normal or decreased |
| Sodium Balance | Variable | Negative | — |
| Body Weight | Increased | Decreased | Normal or decreased |
| Cardiac Filling Pressures | Increased or normal | Decreased | Normal or decreased |
| Hematocrit | Decreased | Increased | Normal or decreased |
| Blood Urea Nitrogen/Creatinine | Decreased or normal | Increased | Normal or decreased |
| Blood Pressure | Normal | Postural hypotension | Normal or decreased |
| Heart Rate | Normal | Tachycardia | Normal or tachycardia |
| Other Criteria | Normal thyroid, adrenal, and renal function; no peripheral edema; no dehydration | Signs and symptoms of volume depletion | Urine volume >3 L/day |