| OBJECTIVE Trigeminal neuralgia refers to neurogenic pain that occurs in the area dominated by the trigeminal nerve.It is usually characterized by recurrent episodes of paroxysmal severe pain.It is one of the most common cranial nerve diseases,which seriously affects the quality of life of patients.Primary trigeminal neuralgia refers to trigeminal neuralgia where the exact cause cannot be found.Since 1967,Dr.Jannetta first reported that microvascular decompression for primary trigeminal neuralgia can achieve good clinical results,many scholars both domestic and foreign have also confirmed the effectiveness of microvascular decompression,thus confirming vascular compression of the trigeminal nerve is one of the important causes of primary trigeminal neuralgia.Microvascular decompression is also the most effective method for the treatment of primary trigeminal neuralgia because it can protect blood vessels and nerve function and is highly effective.In microvascular decompression of trigeminal neuralgia,the most common responsible vessel is the superior cerebellar artery or the anterior inferior cerebellar artery and its branches.With the accumulation of surgical experience,the understanding of the incidence of trigeminal neuralgia caused by venous compression has gradually deepened.The venous blood vessels responsible for trigeminal neuralgia have been recognized,but the surgical strategy for venous trigeminal neuralgia remains controversial.The purpose of this study was to retrospectively analyze the medical records and surgical data of patients with trigeminal neuralgia who underwent surgery in our hospital from January 2012 to December 2017,to study the anatomical relationship between the superior venous complex and the trigeminal nerve,to explain the anatomical classification of venous trigeminal neuralgia,and to explore individualized surgical strategies and therapeutic effectsMETHODS Patients with venous trigeminal neuralgia who were diagnosed and treated in our hospital from January 2012 to January 2017 were selected as the subjects.The criteria for enrollment were:typical clinical manifestations of trigeminal neuralgia and diagnosis of primary trigeminal neuralgia;pain was poorly controlled by drug treatment,or patients cannot tolerate side effects of drugs,and their lives and work were seriously affected;neuroimaging examinations suggest that there are no massive lesions in the brain but signs of neurovascular conflict within the intracranial segment of the trigeminal nerve;severe comorbidities or abnormal damage to important organs such as heart,lungs,kidneys,and uncorrected,can tolerate the operation;intraoperatively confirmed vein as a single responsible vessel,or as the main responsible vessel together with artery to participate in NVC.A total of 64 patients,aged 28-69 years,with an average age of(54.8 ± 9.6)years,included 23 males,41 females,and a history of trigeminal neuralgia between 18 and 192 months,with an average of 54 months.Among them,19 patients had previously received radiofrequency thermocoagulation of trigeminal gasserian ganglion or gamma knife treatment,but the treatment was not effective.Preoperative symptomatic assessment:12 cases of pain in the second branch of the trigeminal nerve(V2),16 cases in the range of the third branch(V3),36 cases in the range of the Ⅱ and Ⅲ(V2,V3),no patient with pain in the first branch of the trigeminal nerve(Ⅵ).Preoperative imaging evaluation:Except for one patient who underwent coronary stent implantation previously could not perform MRI,but performed CT scan,head and neck CTA examination,all the other 63 patients underwent cranial MRI,especially three-dimensional trigeminal magnetic resonance tomographic angiography(MRTA)examination.Combined intravenous and inhalational general anesthesia was applied for each patient.the patient took the lateral position and the head was rotated to the lateral side naturally.The root of mastoid was placed at the highest point in the surgical field.The design of skin incision was approximate 5-8 cm straight line parallel to the postauricular hairline,one-third above the superior nuchal line and two-thirds below the superior nuchal line.Drilled a hole at the lower edge of the transverse-sigmoid sinus junction,and milled a circular-shaped bone flap with a diameter of about 3 cm.A T-shaped dural incision was made with the vertical tip of the "T" toward the junction of the sinuses.Under the microscope,the arachnoid membrane of the cerebellopontine cistern was dissect sharply and the cerebrospinal fluid was released.The cerebellar hemisphere was retracted mildly by the aspirator as the "micro-brain platen".The arachnoid membrane surrounding the superior petrosal vein complex(SPVC)was sharply separated,and its anatomical shape and relationship with the trigeminal nerve root were observed.Then the surgical corridor was chosen between the infratentorial supracerebellar approach and suprafloccular transhorizontal fissure approach depending on the anatomy characteristic of superior petrosal vein complex.Based on the anatomical features of intraoperative superior venous complex and its positional relationship with the trigeminal nerve,the supenor venous complex was divided into four types.First,the superior petrosal vein complex can be divided into two subtypes:superficial and deep.The most common branch of superficial superior petrosal vein complex is the transverse pontine vein,vein of the middle cerebellar peduncle,and often directly drain into the superior sinus;The deep superior petrosal vein complex is mainly composed of the cerebral trigeminal vein,the cerebellar hemisphere superior vein,vein of the cerebellopontine fissure,and is first merged into a trunk of superior petrosal vein and then drain into the superior petrosal sinus.Second,superior petrosal vein complex was divided into 2 subtypes according to the location of the venous empty point:the lateral and the medial.The lateral type is between the lateral limit of the trigeminal nerve and medial limit of the internal auditory meatus,while the medial type is above or medial to the boundaries of Meekers cave.In summary,the superior petrosal vein complex is divided into the following four types:type Ⅰ:superficial superior petrosal vein complex,the point of entry is located the lateral limit of the trigeminal nerve and medial limit of the intermal auditory meatus;type Ⅱ:superficial superior petrosal vein complex,the point of entry is located above or medial to the boundaries of Meckel’s cave;the type Ⅲ:deep superior petrosal vein complex,the point of entry is between the lateral limit of the trigeminal nerve and medial limit of the internal auditory meatus;the type Ⅳ:deep superior petrosal vein complex,the point of entry is located above or medial to the boundaries of Meckel’s cave.On this basis,we choose a reasonable surgical approach in order to more fully explore the trigeminal nerve without injury to the vein:type Ⅰ-suprafloccular transhorizontal fissure approach,type Ⅱ-infratentorial supracerebellar approach,type Ⅲ-infratentorial supracerebellar approach or suprafloccular transhorizontal fissure approach,and type Ⅳ-combination of infratentorial supracerebellar approach and suprafloccular transhorizontal fissure approach.The diameter of the responsible veins was divided into three types:fine(diameter<1.Omm),medium(diameter≥1.0mm,and<3.0mm),eoarse(direct≥3.0mm).The locations of neurovascular conflict(NVC)were divided into three types:the trigeminal nerve root(root entry zone),cistern segment,and near the Meckle’s cave.The degree of vascular compression nerves can be divided into three types:simple neurovascular contact(nerve compression by blood vessels,but no obvious displacement or distortion),neurovascular contact with displacement(displacement or distortion of the trigeminal nerve at the site of a neurovascular contact),severe neurovascular contact(neurovascular contact with displacement or atrophy).After the arachnoid between the trigeminal nerve and the responsible vessel was dissected and the anatomical features and spatial relationship were fully revealed,several factors of the above NVC were comprehensively evaluated to decide which decompression method to adopt.In view of the case of the supra-rock complex as a single-responsible blood vessel,we use the following decompression method:1.For thick veins,such as the stem of the superior petrosal vein(SPV)or the dilatate transverse pontine vein(TPV),which were usually observed as parallel,riding,or even twining compression at the TRZE,the transpose method is used by using a Teflon sling attached to petrosal dura need aid of medical adhesive,and interpose method can be supplement to ensure the effect of decompression sometimes.2.For medium size veins,such as the pontotrigeminal veins,the veins of the cerebellopontine fissure,or the middle cerebellar peduncle,which usually manifest as moderate compression at the TRZE,direct interpose Teflon felt can be sufficient enough.3.For common stems of the veins draining into the lateral part of the cerebellar hemisphere and emptying into the SPV,or directly into the superior petrosal sinus,because the distance between them and the Meckel’s cave was short and the space for transposing is too narrow,we used the interpose method.For thin perforator veins,we performed not sacrifice but interposing little Teflon felt.4.Small vein compression of the trigeminal nerve root or combined with perforating vein,which were difficult to pulled away from the nerve,internal neurolysis of the trigeminal nerve sensory root was conducted:combed the trigeminal sensory root by using a special gun-shaped corneal incision along the longitudinal axis for about 5 times,meanwhile,the anesthesiologist closely observed the changes of vital signs.When encountered with dual NVC of artery and vein,we first decompressed arteries,and then dealt with the veins.After decompression or internal neurolysis was completed,and there was no bleeding in the surgical field,the dura mater was tightly sealed,the muscles and lesser occipital nerve were replaced respectively,fascia and scalp were sutured layer by layer.Postoperative evaluation:The pain degree scale and facial numbness scale of the Barrow Neurological Institute was used to evaluate the efficacy before discharge and long-term follow-up after discharge.BNI pain levelⅠ～Ⅱ was considered as effective,and the situation that postoperative pain was first relieved but gradually aggravated to grade Ⅲ～Ⅳ was defined as recurrence.RESULTS By reviewing the preoperative evaluation results and surgical findings,a total of 64 patients with venous trigeminal neuralgia were enrolled in this research.In the preoperative imaging evaluation,CT or MRI confirmed that there was no intracranial massive lesion.MRTA showed that 47 patients had clear neurovascular compression at the root of the trigeminal nerve and 16 patients had suspicious neurovascular compression.The most frequent responsible vessel was the trunk of superior petrosal vein or its branches,13 cases of simple vein compression and 51 cases of arteriovenous compression.According to the anatomical type of the responsible vein,the surgical path was selected:28 cases of type Ⅰ,through the suprafloccular transhorizontal fissure approach;25 cases of type Ⅱ,through the infratentorial supracerebellar approach;4 cases of type Ⅲ,of which 3 cases through the suprafloccular transhorizontal fissure approach,and 1 case through the infratentorial supracerebellar approach;7 cases of type Ⅳ were combined with two surgical approaches to complete the operation through different venous corridors.The spatial relationship between the vein and the trigeminal nerve:30 cases(46.9%)in the ridding type,18 cases(28.1%)in the penetrating type,8 cases(12.5%)in the surrounding type,5 cases(7.8%)in the parallel type,and 3 cases in the compound type(4.7%).Follow-up:After the operation,the patients were evaluated for efficacy.34 patients(53.1%)with complete pain disappeared,17 patients(26.6%)had significant pain relief,and 13 patients(20.3%)had partial pain relief.Long-term follow-up after discharge,followed up for 6 to 60 months(6 patients lost after 6 months),the simple venous group and arteriovenous group were separately evaluated:1.simple vein type,9 cases(69.2%)were excellent,1 case(7.7%)was good,2 cases(15.4%)were general,1 case(7.7%)was poor;2 arteriovenous combination type,33 cases(64.7%)were excellent,8 cases(15.7%)were good,7 In the case of example(13.7%),3 cases(5.9%)were poor.The main postoperative complications included 7 cases of facial numbness(10.9%),including 1 cases of simple decompression and 6 cases of intermal neurolysis,but did not affect lives;1 case of intracranial infection(1.6%),discharged after successful anti-infective treatment and continues lumbar drainage;1 case(1.6%)of high-frequency hearing loss,totally recovered after neurotrophic treatment and hyperbaric oxygen therapy.CONCLUSIONS Microvascular decompression has a good efficiency on the treatment of venous trigeminal neuralgia.The surgical plan for venous trigeminal neuralgia needs to be combined with preoperative evaluation and intraoperative findings.Preoperative imaging examination can provide a reference for the relationship between the responsible blood vessel and the trigeminal nerve root.During the operation,the appropriate surgical path is selected according to the anatomical type of the SPVC,and the anatomy of the NVC is judged,and a reasonable vascular decompression or sensory root combing is performed.Protecting SPVC can reduce the risk of postoperative vascular complications.Vascular decompression has a good effect on venous TN;IN is an effective alternative for the treatment of venous TN,but due to the small number of cases,it still needs further study in future work. |
PDF Full Text Request