Spontaneous intracranial hypotension: Two cases including one treated with epidural blood patch

Spontaneous intracranial hypotension (SIH) is characterized by orthostatic headache (OH), low cerebrospinal fluid (CSF) pressure, and diffuse pachymeningeal gadolinium enhancement (DPME). We present here the case studies of two patients. One patient demonstrated a CSF leak in the mid-thoracic region, and recovered completely with conservative treatment. The other patient in whom leak could not be demonstrated, developed dementia, rapidly worsening encephalopathy, and became comatose, necessitating urgent epidural blood patch (EBP) with 25 cc of autologous blood, after which immediate and complete symptomatic relief was obtained. A second EBP was required a few days later and also provided complete and sustained clinical benefit, without subsequent recurrence. Both patients had OH and showed bilateral subdural fluid collections, DPME and “sagging” of brain on MRI. A high index of suspicion, recognizing the orthostatic nature of headache, and typical findings on contrast enhanced MRI should point to the diagnosis of SIH. EBP can be effective treatment in patients unresponsive to conservative measures.


Introduction
Spontaneous intracranial hypotension (SIH) or syndrome of spontaneous cerebrospinal fl uid (CSF) hypovolemia is characterized by orthostatic headache (OH), low CSF pressure, and DPME (diffuse pachymeningeal gadolinium enhancement) on magnetic resonance imaging (MRI), in the absence of head trauma or lumbar puncture. [1,2] OH, as defi ned by the International Headache Society, is a headache that occurs within 15 minutes of an upright position and is relieved within 30 minutes of recumbency. [3] Almost all cases of SIH are a result of spontaneous spinal CSF leakage from spinal meningeal diverticula or simple dural tears. [1,2] Epidural blood patch (EBP) is the mainstay of treatment when conservative measures fail. Although well described from other parts of the world, there exists a remarkable paucity of reports of SIH from India. We could identify only one case series of this condition from India [4] and no report of a patient treated with EBP. We report two cases of SIH, one of whom was treated successfully with EBP.
posterior fossa is a specifi c imaging feature of SIH, [2] and was also seen in both patients. The headache is a result of downward displacement of the brain due to loss of CSF buoyancy, causing traction on pain-sensitive structures, particularly the dura. Though classically 'orthostatic', headache in SIH may be of a variety of patt erns: non-orthostatic, chronic daily, exertional, acute "thunderclap", paradoxical (increased on recumbency) or even absent.
In the fi rst patient (Case 1), routine MRI spine revealed a CSF leak at the level of the sixth thoracic vertebra. The thoracic spine is the most common site of a CSF leak in SIH. [1,2] However, in most cases, MRI may show only extra-arachnoid fl uid collections over several levels, or CSF extravasation into paraspinal soft tissues over

Case 2
A 50-year-old male presented with a new onset, diff use bifrontal and occipital, orthostatic headache since two months. Headache would worsen markedly within a few minutes of assuming an upright position. He had become progressively dull and apathetic, and was incontinent for urine since the last few weeks. He had vomited twice in the last week. On examination, he was conscious, but withdrawn and inatt entive. Fundi were normal, lower limb refl exes were exaggerated and plantars were extensor. Rest of the neurological examination was normal. MRI brain showed bilateral thin subdural fl uid collections and DPME [ Figures 1B and 1C]. Routine MRI spine did not reveal a CSF leak. He was treated with bed rest and hydration. A few days aft er admission, he became progressively more drowsy, and later unresponsive, with poorly reactive pupils, and a decerebrate response of the left upper limb to pain. As an emergency measure, 25 cc of autologous blood was injected into the L3-L4 epidural space, followed by placement in the Trendelenburg position. Within a few hours, he became fully conscious, alert and responsive. Four days later, he became drowsy again. A repeat EBP with 30 cc of blood was performed, with improvement in sensorium over the next few hours. There was no subsequent recurrence and he remained asymptomatic thereaft er.

Discussion
Both our patients had orthostatic headache (OH) as defi ned by the International Headache Society, without prior head trauma or lumbar puncture. In both cases, we observed subdural fl uid collections and DPME on MRI, the two most common imaging features of SIH. [2] Downward descent (sagging/sinking) of the brain with eff acement of subarachnoid cisterns and crowding of fewer levels. Demonstration of the exact site of the leak, such as was seen in our case, is uncommon. A year later this MRI spine fi nding remained unchanged despite disappearance of clinical symptoms and improvement of brain imaging fi ndings. It is conceivable that a degree of functional "closure" of the dural rent had occurred due to alteration of CSF fl ow dynamics over time, although its anatomic correlate had curiously remained unchanged. It is also intriguing that this patient with the larger, easily demonstrable, persistent CSF leak improved with bed rest, while the other patient (Case 2), in whom leak could not be demonstrated, worsened rapidly and needed treatment with EBP. More sensitive tests such as spinal CT myelography and radioisotope cisternography would have been useful in demonstrating the location of CSF leak [1,2] in Case 2. However, we were unable to perform these tests because of rapid clinical worsening a few days aft er admission, necessitating urgent therapeutic intervention.
Other common symptoms in SIH include neck/back pain and nausea (noted by our patients), altered sound perception, dizziness, diplopia and other visual, facial sensory, and radicular limb symptoms. Although rare, a reversible frontotemporal patt ern of dementia has been described in SIH. [5] Reversible encephalopathy, stupor, and coma due to diencephalic compression have also been reported in several patients. [6] Case 2 in our study had developed a similar predominantly frontal lobar aff ection with apathy and abulia, and went on to become comatose with signs of brainstem herniation. All these features resolved promptly and completely aft er EBP.
The first patient (Case 1) had a history of shoulder dislocation a few years ago, and in him we noted marfanoid features. Approximately one-fi ft h of patients with SIH have subtle skeletal manifestations of Marfan syndrome, such as tall stature, arachnodactyly, high arched palate, and joint hypermobility, but none of the other stigmata of the syndrome. [7] These patients do not harbor fi brillin gene mutations, but a defect of microfibrils, important components of extracellular matrix associated with fi brillin, has been demonstrated. [7] Other connective tissue disorders may also predispose patients with SIH to dural weakness, and hence to a spinal CSF leak. [2] The underlying mechanism of the syndrome of SIH is probably neither CSF hypotension nor CSF hypovolemia per se, but rather an altered distribution of craniospinal elasticity due to spinal CSF loss, and "spontaneous spinal CSF leak" seems the preferred descriptive term. [8] We did not perform a CSF study on our patients as we felt that additional violation of the dura could worsen the underlying CSF leak.
All cases are usually treated conservatively with bed rest (which is also what the patient prefers anyway) and adequate hydration. [1,2] The leak may stop spontaneously in some patients, who recover regardless of treatment. Caffeine, theophylline and corticosteroids are also tried but no approach is of proven effi cacy. Given time, these conservative measures are probably effective in many patients. EBP is the defi nitive treatment in those who fail to respond to conservative measures. [1,2] 20 cc of autologous blood is injected into the lumbar epidural space, aft er which the patient is placed in the Trendelenburg position for approximately two hours. [9] This allows the blood to ascend over several segments to seal the leak. The eff ect of EBP is twofold: an early eff ect related to volume replacement resulting from dural tamponade, and a latent eff ect that results from sealing of the leak. [9] The patient we treated with EBP probably benefi ted from both these mechanisms, as he had both immediate and long-lasting symptomatic relief. In spontaneous CSF leaks the success rate with each EBP is approximately 30%, while in CSF leaks following lumbar puncture, where the exact site is known and the anatomical defect is relatively simple, each EBP has a 90% chance of being eff ective. [9] A larger volume of blood (20−100 ml) may be used in cases that fail to respond to the initial patch, but this may cause back pain and radiculopathy. If the exact site of leak is known, a directed EBP or percutaneous placement of fi brin sealant may be of help. [2] Surgical repair of the dural defect may be considered in patients who fail two to three EBPs, and works best in cases where a structural defect or a focal CSF leak is identifi ed. Suturing a leaking meningeal diverticulum or a dural rent, or closing a dural hole by placement of a muscle pledget, can be performed. [2] A transient rebound intracranial hypertension may be seen in some patients. [1] Recurrence of headache is seen in 10%. [2] The prognosis in most cases is good, as we noted in both our patients.
In summary, we describe clinical features, MRI fi ndings, treatment and outcome in two cases of SIH. Reversible dementia, encephalopathy, and coma may rarely be encountered in SIH. A high index of suspicion, recognizing the orthostatic nature of headache, and typical fi ndings on contrast enhanced MRI, such as bilateral sudural eff usions and diff use pachymeningeal enhancement, should lead one to the diagnosis. In patients not responding to conservative measures, EBP may provide eff ective treatment.