Pituitary abscess is a rare infectious disease of the saddle. Its incidence is extremely low, less than 1% of pituitary disorders [1, 2]. The common causes are [1-5]: (1) direct spread of meningitis, osteomyelitis around the pterygoid sinus, paranasal sinusitis, thrombophlebitis of the cavernous sinus, and cerebrospinal fluid nasal leakage into the saddle; (2) infection foci in other parts of the body, caused by the blood route; (3) secondary to other lesions in the saddle such as pituitary adenoma hemorrhage, necrosis, Lachrymal cyst or craniopharyngioma; (4) secondary to surgery in the saddle area. The common causative organisms are Gram-stain positive cocci, others include Gram-stain negative bacteria, Escherichia coli, anaerobic bacteria, fungi, etc. Although CT and MRI scans have certain features, they are still difficult to distinguish from certain pituitary lesions and can be easily overlooked, and preoperative diagnosis is very difficult. Since inflammatory tissue not only compresses the normal pituitary gland, but also the inflammatory damage is often irreversible, once misdiagnosed for a long time, it is difficult to recover from symptoms such as visual acuity, visual field damage and pituitary hypoplasia caused by pituitary abscesses. Therefore, early diagnosis of pituitary abscesses should be highly valued by front-line clinicians. An elderly female patient was admitted to the hospital with “headache with blurred vision for 3 months” and had a history of diabetes mellitus for more than 10 years, and was diagnosed with non-functional pituitary adenoma by preoperative cranial MRI and endocrine examination. Six months later, the patient developed headache again without fever and cerebrospinal fluid nasal leakage, and then the headache continued to worsen and developed into severe headache and vision loss and diplopia after one month. Cranial MRI showed an intra-saddle cystic occupying lesion with iso-signal in T1 image and high signal in T2 image, and enhancement scan showed uniform circumferential enhancement. An intra-saddle pituitary abscess was considered. Single nostril pterygoid sinus approach abscess removal was performed again, intraoperative white pus in the saddle was confirmed, repeated flushing, postoperative broad-spectrum antibiotic treatment, and the abscess disappeared on repeat MRI half a month later, and healed and discharged. Disease characteristics 1. Unlike other diseases of the pituitary gland, the onset of pituitary abscess often has certain causative factors: ① Immune depression caused by systemic diseases, such as severe injury or shock, diabetes mellitus, uremia, leukemia, hypoproteinemia or massive hormone consumption. ② Local factors: pituitary lesions (such as pituitary tumor, craniopharyngioma, Rathke’s cyst, etc.), pituitary surgery and radiation therapy for pituitary diseases can disrupt the local blood circulation of the pituitary gland and reduce the resistance of the pituitary gland to pathogenic bacteria, which can also increase the incidence of pituitary abscess. 2. Similar to other intra-saddle occupying lesions, the clinical manifestations of pituitary abscess mainly include symptoms of tumor compression and hypopituitarism. Although pituitary abscess is a typical infectious disease, it often lacks clear symptoms of fever and meningeal irritation due to the limited lesion. Compared to other pituitary lesions, its clinical symptoms and signs have the following characteristics: (1) the headache caused by pituitary abscess is more intense, probably due to inflammatory irritation and increased intersaddle tension. (ii) Due to the destructive effect of the abscess, patients mostly present with hypopituitarism, which in severe cases may cause total hypopituitarism rather than hormonal hypersecretion syndrome. (iii) Visual field impairment is manifested at an early stage, and depending on the speed of abscess development, it may show progressive vision loss or rapid development, which needs to be distinguished from pituitary tumor stroke. ④Ocular motility disorders such as diplopia, intraocular obliquity, and ptosis are easily seen, which are related to abscess invasion of the motoneurotic and abducens nerves. ⑤ Often combined with cerebrospinal fluid leakage, especially in patients after transnasal butterfly surgery, pay attention to identify whether there is nasal leakage of cerebrospinal fluid. (6) A few patients may have fever, malaise, chills and other signs of peripheral infection. (7) Some patients may show signs of intracranial infection such as headache, nausea, vomiting, high fever, and neck resistance. 3. Endocrine examination may show a decrease in blood PRL, GH, ACTH, LH, FSH, TSH and other hormone levels. Peripheral blood leukocytes may be normal or elevated, and some patients may have accelerated sedimentation and increased C-reactive protein [6]. Cerebrospinal fluid examination may show an increase in leukocytes and protein, with little or no change in sugar and chloride. The most common signs on CT scan are enlargement of the pterygoid saddle and destruction of the pterygoid saddle bone, and soft tissue shadows can be seen in the saddle as well as on the saddle.CT enhancement scan lesions are mostly unevenly enhanced, and a few can be circumferentially enhanced. In magnetic resonance scans, the normal pituitary stalk disappears and there is an occupying lesion in the saddle or suprasaddle. Due to the different protein content in the abscess, the T1-weighted image can be low signal or slightly high signal, and the T2-weighted image can be isosignal or high signal, mostly heterogeneous enhancement, and a few can be circumferential enhancement, accompanied by inflammatory manifestations such as mucosal thickening in the pterygoid sinus [5-7]. Treatment In patients diagnosed with pituitary abscess, surgery should be performed as early as possible, and conservative treatment with drugs alone is mostly ineffective. Only when the patient’s general condition is poor and cannot tolerate surgery, conservative treatment such as nutritional support and anti-inflammatory therapy can be actively performed first, and then surgery can be performed at an optional stage when the condition is stable. In view of the complex neurovascular structure of the saddle area, pituitary abscesses cannot be completely removed like abscesses in other parts of the body, and craniotomy is likely to cause the spread of infection and aggravate the infection, and incomplete removal of cysts is likely to cause recurrence of abscesses and postoperative nerve adhesions resulting in serious complications such as damage to the optic nerve, so transfrontal surgery should be avoided as much as possible for patients suspected of pituitary abscesses. For patients with intra-saddle or mild supra-saddle extension, transsphenoidal approach to pituitary abscess removal is the best option, which can completely remove the abscess and reduce the chance of pituitary damage, while avoiding the spread of abscess caused by the abscess communicating with the subarachnoid space [6, 8, 9]. Intraoperatively, the abscess cavity and the pterygoid sinus are repeatedly flushed with large amounts of saline, hydrogen peroxide and antibiotic solution. At the same time, care was taken to protect the normal pituitary tissue and avoid damaging the saddle septum to avoid cerebrospinal fluid nasal leakage and secondary intracranial infection. After the operation, foreign bodies such as gelatin sponges should be avoided in the saddle and pterygoid sinus. Antibiotics should be used for 3-4 weeks after surgery. Before bacteria are detected, broad-spectrum antibiotics that can easily pass the blood-brain barrier can be used according to the condition, and appropriate adjustments should be made after the results of bacterial culture and drug sensitivity test are available. For patients with pituitary hypoplasia, hormone replacement therapy should be used. Key points 1. Low incidence, often combined with systemic diseases leading to immune deficiency, or a history of previous pituitary surgery or radiation therapy. 2. The clinical manifestations of headache are more intense, and early visual field disorders, diplopia, eyelid ptosis and other ocular motility disorders are easily seen, and some patients may have fever, malaise, chills and other signs of peripheral infection. 3. Endocrine examination mostly shows hypopituitarism rather than hormone overproduction syndrome. 4.The lesion is cystic in CT or MRI scan, with loss of high signal in the posterior pituitary lobe and typical lesions showing ring-like enhancement. 5.If pituitary abscess is suspected, transfrontal surgery should be avoided as much as possible, and transsphenoidal approach can effectively avoid the spread of infection into the skull. 6, strengthen nutritional support and symptomatic treatment, for patients with combined pituitary hypoplasia, hormone replacement therapy should be used. Blind spot 1. Urogyria is considered an important indicator for differentiating pituitary abscess from pituitary adenoma, which has urogynous symptoms in only 10% of patients. Patients with pituitary abscesses often present earlier and their incidence is higher. 2. When patients with cystic lesions in the saddle area have sudden worsening of symptoms and severe pain, the possibility of pituitary cysts should be considered and differentiated from pituitary tumor strokes. 3, DWI in MRI helps to diagnose pituitary abscess, but it is difficult to distinguish it from pituitary stroke and cystic pituitary tumor, so it needs to be considered in combination with endocrine examination and clinical manifestations. 4, Once pituitary abscess is found intraoperatively, pay attention to the process of specimen collection and bacterial culture to avoid secondary contamination and misleading the choice of postoperative antibiotics. 5. In addition to preoperative and postoperative strengthening of antibiotics, nutritional support and symptomatic treatment should be enhanced for patients with decreased immunity, and hormone replacement therapy should be used promptly for patients with combined pituitary hypoplasia. Clinical aphorisms 1. Pay attention to the medical history and carefully follow up whether there is a history of recurrent fever, especially a history of autoimmune disease and inflammation of the pterygoid sinus. 2. Pay attention to the sequence of symptoms and the change pattern of each hormone level, and make a comprehensive analysis and judgment. 3. Carefully read the details of imaging data to analyze and identify the different points of various pituitary diseases.