Definition of liquor
CSF is a clear and colorless fluid that permeates the central nervous system, protecting the brain and spinal cord from any trauma.
Circle of liquor
The CSF is produced inside the cerebral ventricles, precisely at the level of the chorioid plexuses (formed by specialized ependymal cells). Circulating along the brain ventricles, the CSF reaches the sub-arachnoid space, the area between the pia mater and the arachnoid of brain and spinal cord. Let us briefly recall that the arachnoid and the pia mater (leptomenynx), together with the dura mater (pachymeninge), envelop the CNS and the initial tract of the nerves.
The cerebrospinal fluid, which flows caudally, is absorbed by the arachnoid villi (trabeculae that branch off from the arachnoid), subsequently poured into the venous sinuses.
Cerebral ventricles → chorioid plexuses (CSF production) → sub-arachnoid space between arachnoid and pia mater → arachnoid villi → discharge of CSF into the venous sinuses
Functions
Liquor fulfills several, very important, functions:
- It protects the brain and spinal cord from any trauma. In textbooks it is not uncommon to find the expression "the brain floats in the liquor" or "the liquor acts as a cushion for the brain." These two phrases, at first glance absurd, are metaphors that best express the main function performed by the cerebrospinal fluid: protect the CNS from impact or trauma against the bone structures that contain it. The brain weighs approximately 1,300-1,400 grams; however, floating in the CSF (thus receiving an Archimedes thrust) the brain has an "effective" weight of 25-50 grams.
- Nourishes the CNS: the liquor is the vehicle for distributing nutrients in the central nervous system. In other words, the cerebrospinal fluid participates in the exchange of metabolites and nutrients between the brain and blood.
- It contributes to the regulation of intra-cranial pressure and prevents cerebral ischemias. The liquor, in fact, adjusts its volume to changes in blood flow and cerebral mass: by doing so, it keeps both the pressure and the intracranial volume constant.
Chemical composition
The CSF analysis provides relevant information on the general health of the CNS: the alteration of the chemical characteristics of the CSF is often synonymous with ongoing disease / infection.
A sample of cerebrospinal fluid can be collected by spinal tap (or lumbar puncture), a surgical strategy that involves the insertion of a needle between the third / fourth or fourth / fifth lumbar vertebrae. Once the subarachnoid space is reached, we proceed with the collection of a sample of liquor.
Although it derives from blood by a complex ultrafiltration mechanism, CSF has a completely different chemical composition from that of plasma.
Water, oxygen and carbon dioxide easily flow from the blood to the liquor through passive diffusion, through the membranes, while some ions (magnesium, chlorine, calcium, bicarbonate, sodium, potassium) reach the liquor with extreme difficulty.
To assess the integrity or impairment of the CNS, the CSF is analyzed in its different qualitative and quantitative aspects. The main parameters analyzed in the CSF are: color, cell count, glucose and protein levels, presence of antibodies and pathogens.
Healthy liquor
The following are the main characteristics of a healthy CSF: a possible alteration is often synonymous with a pathology or infection in progress.
Parameters analyzed
Reference range for healthy liquor
APPEARANCE AND COLOR
Transparent, defined as rock water (or rock)
CHLORIDES (Chlorurorrachia)
700-750 mg / dl or 115-130 mEq / L
WHITE BLOOD CELLS
3 (all mononuclear)
RED BLOOD CELLS
0
GLUCOSE (glycorrachia)
50-80 mg / dL (equal to 2/3 of blood sugar)
GLUTAMINE
6-15 mg / mL
LACTATE
10-40 mg / dL in infants
10-25 mg / dL in older children and adults
Between 2.0 and 7.2 U / mL
pH
Included in the range of 7.28-7.32
LIQUOR PRESSURE
- 10-18 cm H2O (8-15 mmHg): with patient lying on his side
- 20-30cm H2O (16-24 mmHg) with patient seated
- 8-10 cm H2O in infants
15-45 mg / dL. In some cases a proteinorrachia of 60 mg / dL is also acceptable
Clearly, the absence of pathogens and tumor cells in the CSF also indicates a healthy CSF.
Altered liquor
The variation of the normal qualitative and quantitative parameters of the liquor, shown in the table, must immediately alert. Spinal cordesis is an exceptional diagnostic strategy, which allows the collection of a CSF sample: the subsequent analysis of the cerebrospinal fluid offers a general picture of the degree of integrity of the CNS.
What are the possible morbid conditions associated with an ABNORMAL LIQUEUR?
The most frequent pathologies detectable by the liquor analysis are:
- Infections: encephalitis, meningitis
- Autoimmune diseases: meningeal sarcoidosis, multiple sclerosis, Guillan-Barrè syndrome
- CNS neoplasms
What does a DECREASE OF GLUCOSE in the liquor symbolize?
The decrease in glycorrachia is the light on for:
- Sub-arachnoid hemorrhage (or hematoma)
- Hypoglycemia
- Bacterial or fungal meningitis
- Meningeal metastases
- Tuberculosis
What is the pathological significance of a leukocyte-rich liquor (LEUCOCYTOSIS)?
Detection of reactive leukocytosis in CSF may indicate:
- Parasitic infections
- Meningitis
- Meningoencephalitis (from heartworm)
- Polyneuritis (inflammatory process involving multiple nerves at the same time)
- Meningeal sarcoidosis
- Multiple sclerosis
- Guillain-Barrè syndrome
What pathologies can be hidden behind an INCREASE IN polymorphous NEUTROPHILS nucleated in the liquor?
- Brain abscess
- Convulsions
- Hemorrhages
- Subdural empyema (pouring of blood into the space between the arachnoid and dura mater)
- Encephalitis
- Bacterial / viral / fungal / tuberculous meningitis
- Neoplasms
What pathologies are suspected when a MONOCYTOSIS is revealed (increase in the number of monocytes) in the liquor?
- Intracranial hemorrhage
- Cerebral infarction
- Syphilitic / viral / fungal / bacterial meningitis
- Neoplasms
What can a REDUCTION in the concentration of LACTATE in the liquor hide?
A reduction in the concentration of lactate in the liquor is an indicator of pathologies such as:
- Cerebral atherosclerosis
- Colon cancer (late stage, metastasis)
- Convulsions
- Intracranial haemorrhage → the increase in lactate dehydrogenase (LDH) in the CSF is also a sign of intracranial haemorrhage
- Hypotension
- Injuries / trauma
- Bacterial meningitis (especially from mycoplasma) → further confirmation of meningitis is obtained from the "increase of" LDH in the CSF
