Idiopathic intracranial hypertension  was first formally described in 1893. The syndrome has been referred to as brain swelling of unknown cause, papilloedema of indeterminate aetiology, pseudotumour cerebri and benign intracranial hypertension and, more recently, ‘idiopathic intracranial hypertension' has been used. The description ‘benign’ is a misnomer as the condition, if not treated, can lead to loss of vision. The diagnosis is one of exclusion; following normal contrast-enhanced computerised tomography or magnetic resonance imaging, a lumbar puncture is performed to confirm a raised lumbar cerebrospinal fluid (CSF) opening pressure > 250 mmH2O with a normal CSF composition [1, 2]. Idiopathic intracranial hypertension is a rare condition with an overall incidence of 1 : 100 000, but it is more common in women than men (3 : 1) with the highest incidence found in the 20–30 years old age group; it has been reported to have an incidence of approximately 1 : 1000 pregnancies [3, 4]. It is more common in the first and second trimesters. The most common presenting symptoms are manifestations of generalised intracranial hypertension, namely headache and visual obscuration. Diplopia, pulsatile tinnitus, nausea and vomiting may be present in up to 50% of patients, with neck/back/shoulder pain or radicular pain less frequent [1, 2]. The spontaneous abortion rate is not increased, and subsequent pregnancies do not increase the risk of recurrence .
Idiopathic intracranial hypertension is a rare syndrome characterised by prolonged elevation of intracranial pressure in the absence of hydrocephalus, intracranial mass lesion or infection, and with increased cerebrospinal fluid pressure but a normal composition. We report a case of uncontrolled idiopathic intracranial hypertension successfully managed using an intrathecal catheter for analgesia in labour and delivery as well as temporary control of intracranial pressure.
A 28-year-old primigravida, of height 166 cm and weight 92 kg, was referred to an ophthalmologist at 27 weeks' gestation after a 7-day history of deteriorating vision with transient episodes of visual loss, nausea, vomiting and headaches not responding to analgesics. Ophthalmologic examination and visual field assessment showed a reduction in the size of the isopter of the eye. The visual acuity was 6/9 (normal 6/6) in the right eye and 6/5 in the left eye. No relative afferent pupil defect was found, and there was normal colour vision. Both optic disks looked very swollen on fundoscopy, but both foveas appeared healthy. All investigations, including brain scan, were normal. The patient was referred to a neurologist for further management. Diagnostic lumbar puncture was performed in the lateral decubitus position, and the CSF opening pressure was measured at 570 mmH2O; CSF composition was normal. A diagnosis of idiopathic intracranial hypertension was established. Treatment consisted of twice-weekly lumbar puncture from the 28th week of pregnancy, with withdrawal of 30 ml CSF via a 22-G Quincke needle, and bed rest. The neurologist was not keen on medical treatment with steroids or acetazolamide as his opinion was that only frequent lumbar punctures would save the patient's vision.
At the patient's second lumbar puncture, the CSF pressure measured 300 mmH2O. Testing revealed normal colour vision, visual acuity of 6/9 and 6/6 in the right and left eyes, respectively, and only mild papilloedema of the right optic disk. Visual symptoms and signs remained static between 30 and 36 weeks' gestation, and no further therapy was administered. As it was difficult to control her CSF pressure by just twice-weekly lumbar puncture, the neurologist suggested early induction of labour to allow more frequent lumbar punctures, medical therapy and possibly insertion of a shunt. The patient already found it difficult to travel 160 miles each week to see her nearest neurologist, and she was keen on early delivery to comply with the visits. Labour was therefore induced at 37 weeks' gestation. On admission to the delivery suite, the patient reported the continued presence of nausea, headache and visual disturbances. After discussion with the patient, it was decided to provide labour analgesia using an intrathecal catheter with intermittent top-ups. The patient was placed in the sitting position and 18-G Tuohy needle was inserted intrathecally at the L3/4 interspace. A jet of CSF via the Tuohy needle suggested high pressure, so 25 ml CSF was drained, after which only drips were observed. A multi-orifice 19-G epidural catheter was then placed 4 cm intrathecally through the Tuohy needle. With the patient still sitting, 1.0 ml hyperbaric bupivacaine 0.5% was injected intrathecally. Approximately 10 min later the upper level of the sensory block (to cold and pin-prick) was established at T7, associated with a dense motor block. Subsequent top-ups of 1.0 ml of the same solution were given by the anaesthetist approximately every 3 h, providing very effective analgesia. No change in blood pressure or heart rate was noticed after any of the top-ups. The patient did complain of a mild biparietofrontal headache late in the first stage of labour, similar in nature and severity to the headaches she had suffered antenatally. There were no visual symptoms or any other significant findings. Maternal observations remained stable throughout the labour, which proceeded uneventfully. After 13 h a healthy baby was delivered via forceps delivery. The patient received a total of 4 ml hyperbaric bupivacaine 0.5% intrathecally through labour. The intrathecal catheter was removed 2 h after delivery, and the patient returned to the ward. On the first 2 days postpartum, she complained of mild biparietofrontal headache, similar in nature to her antenatal headaches. There were no symptoms suggestive of postdural puncture headache (PDPH). The patient was discharged from hospital and referred to the neurologist for further treatment; she was started on 250 mg acetazolamide 6-hourly with resolution of her headache, and the acetazolamide was discontinued 8 months later. At the time of writing, the patient is 16 weeks pregnant with neither signs nor symptoms of idiopathic intracranial hypertension so far.
There is a paucity of information concerning the anaesthetic management of patients with idiopathic intracranial hypertension, and the impact of pregnancy and labour on the condition. There are three major theories as to the cause of idiopathic intracranial hypertension: increased resistance to absorption of CSF; increased production of CSF; and increased venous sinus pressure . It appears that pregnancy itself does not predispose to this condition, but it has been reported that symptoms often worsen during pregnancy with improvement in symptomatology following delivery or abortion.
Treatment of idiopathic intracranial hypertension involves reduction of intracranial pressure to control symptoms and prevent pressure on the optic meninges and the optic nerve, preserving vision. Serial lumbar punctures have only a 30–40% success rate when used alone; medical therapy, especially with steroids, is effective as the primary treatment in > 80% of cases, although recurrence (∼ 14%) and complications of therapy are significant [7, 8]. Weight reduction with a non-ketotic diet, salt and fluid restriction, and diuretics such as acetazolamide to decrease cerebrospinal fluid production can be used to reduce generalised tissue oedema [7, 8]. The pregnant patient with idiopathic intracranial hypertension has the added concern of fetal well-being. The therapeutic agents of choice may be potentially teratogenic and a dietary regimen of caloric restriction is controversial in this setting. The manufacturers of acetazolamide advise avoidance in pregnancy due to toxicity in animal studies, and the evidence on the safety of systemic corticosteroids in pregnancy is equivocal . In our case, the decision to decline drug therapy had been made by the ophthalmologist, neurologist and patient before any anaesthetic input. Idiopathic intracranial hypertension is a chronic syndrome with a good prognosis and spontaneous remissions do occur. However, in severe cases, aggressive management may be necessary to preserve vision, as 10% of patients with this condition suffer permanent blindness. Surgical intervention via insertion of a lumbar peritoneal shunt or optic nerve sheath fenestration and decompression of optic meninges were not options in our case, due to the risk of surgery in pregnancy. In addition, there had been no regression of her vision and medical treatment had not been tried, so therapeutic lumbar puncture was performed in an attempt to control the symptoms.
As serial lumbar punctures were ineffective in our patient, early induction of labour was necessary to allow additional therapy to preserve patient's vision. Idiopathic intracranial hypertension itself, particularly when asymptomatic, is not an absolute indication for caesarean section , though allowing labour to proceed with good analgesia, and an elective instrumental delivery to minimise surges in intracranial pressure, constitute an accepted alternative. The uterus empties approximately 300 ml blood into the venous system with each myometrial contraction and the resulting rise in central venous pressure, stroke volume, cardiac output and systemic blood pressure is associated with an increase in CSF and epidural pressures, particularly in the second stage of labour. Such increases in intracranial pressure are independent of pain, but exacerbated by skeletal muscle contractions occurring in response to pain . These increases in pressure can be attenuated, but not completely abolished, with effective regional anaesthesia, the technique of choice for analgesia/anaesthesia during labour and delivery in these patients . Epidural analgesia offers control over the spread of the block with the use of an incremental technique, but injection of fluid into the epidural space causes an increase in intracranial pressure for a short time . This surge not only produces unpleasant symptoms for the patient, but could potentially compromise her vision by compressing the optic nerve. There are a few sporadic reports in the literature of successful use of epidural analgesia for labour and spontaneous vaginal delivery in parturient with idiopathic intracranial hypertension . Bedson and Plaat reported the combined spinal–epidural technique for delivery by caesarean section . Unlike other conditions where intracranial pressure is raised due to a space-occupying lesion and the potential risk of tonsillar herniation and coning is a major concern, dural puncture is not contra-indicated in patients with idiopathic intracranial hypertension. Placement of an intrathecal catheter has the advantage of rapid onset of a good quality block, particularly important due to the effect of pain on intracranial pressure. The therapeutic option of CSF drainage via the catheter, if symptoms deteriorated during progressive labour, was also available. The risk of PDPH with deliberate dural puncture, compared to the benefit of having a therapeutic option during labour, was discussed with the patient. Although PDPH requiring epidural blood patch has been reported in a patient with idiopathic intracranial hypertension who received a therapeutic lumbar puncture for CSF drainage , there is growing evidence that intrathecal placement of the epidural catheter may reduce the incidence and severity of PDPH . In addition, we speculate that in our patient the rapid production of CSF would compensate for the loss of CSF into the epidural space.
An intrathecal catheter provides good labour analgesia and a good quality block if operative delivery is deemed necessary . The epidural volumes required for an adequate block for operative delivery may be detrimental in patients with idiopathic intracranial hypertension. If single-shot spinal anaesthesia is selected for caesarean section, the risk of high or even total spinal is possible in patients following removal significant volumes of CSF. A high sensory level was noticed in our case with only 5.0 mg of hyperbaric bupivacaine in the sitting position. If general anaesthesia is selected, the increase in intracranial pressure associated with rapid sequence induction and laryngoscopy, as well as the usual anaesthetic considerations for the parturient, were an obvious concern. We were under the impression (from the obstetrician's point of view) that the patient would be very likely to need surgical intervention. Due to uncertainty about the spread of the local anaesthetic, we thought it best to check the spread using 5 mg of hyperbaric bupivacaine sooner rather than later. We currently use intrathecal catheters in our unit for selected cases, for example, morbidly obese patients in whom epidural analgesia/anaesthesia is less likely to be satisfactory, and those with a history of difficult intubation, in whom we are anxious to avoid general anaesthesia. The catheter can readily and effectively be used for extending the block in case of emergency caesarean section. Though we could be criticised for not measuring the CSF pressure, we opted to keep things as simple as possible and rely on clinical signs and symptoms of increased intracranial pressure – though we were ready to measure the pressure if indicated. Finally, this case illustrates the need for a multidisciplinary approach involving obstetrician, ophthalmologist, neurologist/neurosurgeon and anaesthetist.
We would like to thank Dr Rachel J. Vickers for her support in supplying the necessary information to publish this case report.