OVERVIEW
Intracranial low-pressure syndrome is a clinical syndrome caused by a variety of etiologies, with lumbar puncture cerebrospinal fluid pressure <70 mmH2O in the lateral position and characterized by postural headache.
Etiology
The primary etiology is unknown and may be related to viral infection. Secondary is mainly caused by a large leakage of cerebrospinal fluid or a decrease in cerebrospinal fluid production, such as lumbar puncture, traumatic brain injury and cerebral surgery, etc., caused by continuous leakage of cerebrospinal fluid, shock, severe water loss, cerebral vasospasm, meningoencephalitis, severe systemic infections, poisoning, and cranial radiotherapy cause a decrease in cerebrospinal fluid volume.
If cerebrospinal fluid secretion is reduced or cerebrospinal fluid leakage occurs, it causes intracranial hypotension syndrome. Common causes include choroid plexus injury, post-lumbar puncture, trauma or meningitis. Intracranial low pressure syndrome is categorized as primary or symptomatic. Symptomatic and includes a variety of types, the etiology of each type is not the same, mainly due to the volume of the contents of the cranial cavity is reduced: ① cerebrospinal fluid volume reduction, the most common. ② Decrease in cerebral blood volume. (iii) Reduction in the volume of brain tissue. ④ Primary intracranial hypotension syndrome.
Symptoms
Intracranial low pressure can lead to the following changes:
1. Nociceptive sensitive nerves such as large intracranial blood vessels, sensory nerves and meninges at the back of the neck are deprived of the normal lining effect of cerebrospinal fluid. The manifestations are headache, head swelling, vomiting, discomfort in the forehead and the back of the neck, and cervical tonic symptoms, the most common clinically obvious with upright headache.
2. Reduced cerebrospinal fluid pressure and cerebral vasospasm secondary to the labyrinth of the inner ear and optic nerve sheath. The manifestations are vertigo, nystagmus, blurred vision, diplopia, which is rare clinically.
3. It causes meningeal edema and congestion, so that red blood cells penetrate into the subarachnoid space, and plasma proteins also enter the subarachnoid space. Clinical manifestation is bloody cerebrospinal fluid.
4. Cerebral cortex and hypothalamus dysfunction occurs. Clinical manifestations are lethargy, severe coma, aphasia, respiratory and blood pressure changes, which are very rare clinically and have a very poor prognosis.
Examination
1. Physical examination
Patients often have cervical ankylosis, a few patients may have cerebral nerve manifestations such as facial nerve, trigeminal nerve and motor nerve, and the rest of the neurological examination is negative. There may be mild neck resistance, heart rate slows down when standing upright, and there are often no positive neurological signs.
2. Lumbar puncture examination
The cerebrospinal fluid pressure is lower than 70mmH2O; cerebrospinal fluid examination: it may be normal, or there may be an increase in the number of cells and proteins.
3. CT or MRI examination
(1) Cranial CT: It shows that the ventricular system, cerebral pools and sulci become narrow and shrunken, and the changes of lateral ventricles and suprasellar pools are especially obvious. Subdural effusion can also be seen in some patients.
(2) MRI: It is currently recognized as the preferred non-invasive diagnostic method, but pure MRI is not specific for the diagnosis of this disease, and it is also necessary to carry out cranial MRI enhancement scanning, and the main manifestations are:
(1) Dural thickening and enhancement: diffuse symmetric thickening and linear enhancement of the dura mater is the characteristic manifestation, and both the supratentorial and infratentorial dura mater are involved, with no involvement of the soft meninges, and the thickened dura mater is easier to be observed in the FLAIR image and T1WI than in the T2WI.
(2) Displacement of brain tissues: In low cranial pressure, due to the weakening or disappearance of the water cushion effect of cerebrospinal fluid, brain tissues are displaced by gravity, such as crowding of the posterior cranial fossa and downward displacement of cerebellar tonsils.
(3) Expansion of venous sinuses and cerebral veins: the upper sagittal sinus and sinus confluence sinus cavity are dilated, and the cross-section is “O”-shaped or curved and convex.
(4) Ventricular changes: swelling of brain tissue, narrowing of the ventricles.
(5) Subdural effusion and subdural hematoma: Subdural effusion is considered to be a compensatory response of the intracranial fluid space to the low pressure of cerebrospinal fluid.
6) Enlarged pituitary gland: the above signs will improve or disappear with correction of the low cranial pressure.
7) Others: Spinal MRI manifestations mainly include diffuse enhancement of the dura mater, congestive dilatation of the extradural venous plexus, extradural effusion, abnormalities of the nerve root cuffs, and spinal diverticula showing brain atrophy. Enhanced scanning MRI with gadopentetate dimeglumine (Gd-DTPA) can show diffuse enhancement of the dura mater of the whole brain and vertical brain displacement.
Diagnosis
The diagnosis of this disease is not difficult, as long as we grasp the clinical characteristics of having upright headache and vertigo aggravation, and the symptoms are reduced or disappeared when lying down, and combined with the lumbar puncture cerebrospinal fluid pressure <70mmH2O, and the pressure of the neck without vertebral canal obstruction, the diagnosis can be clearly defined.
Treatment
Patients should be instructed to rest in bed, with the head low and feet high position, and the foot of the bed elevated by 20-30°. Encourage the patient to drink more water, 3000～4000 ml per day. Salt can be added in moderation, preferably saline. Saline or isotonic fluid can be injected intravenously, 1000～1500 ml per day, 3～5 days as a course of treatment.
Drugs such as ephedrine (ephedrine), caffeine, poppy, dexamethasone and neostigmine can be tried as adjuncts to stimulate the production of cerebrospinal fluid. In patients with chronic choroid plexitis, hyaluronidase can be administered intramuscularly to promote dissipation of inflammation.
Because lumbar puncture is a common cause of intracranial hypotension syndrome. Therefore, lumbar puncture operation should strive to standardize the use of fine needles, the puncture process should maintain the patient’s position, avoid movement, and after the puncture to maintain the pillows lying down for more than 6 hours. If the intracranial hypotension syndrome after lumbar puncture is still ineffective after 48 hours of the above treatments, epidural autologous blood repair can be considered, or saline in the epidural cavity can be continuously dripped at a rate of 20 ml/hour for 48 hours, but secondary infection should be avoided. If the above methods are ineffective, surgical repair of the fistula should be performed.