AANS2000AANS2000Internet Outline of

Neurosurgery

E. R. Flotte MD, 2009

 

Please send comments and corrections to admin@flotte2.com

www.outlineofneurosurgery.com

 

 

 

Functional

 

 

 

Movement Disorders

·         Reviews: Rezai AR N2/08S - VIDEO

 

Targets

·         Subthalamic Nucleus (STN): 12mm lateral to midline, 3mm posterior to MC, 6mm below AC/PC plane

·         VIM nucleus thalamus: 11mm from lateral wall 3rd ventricle, few mm anterior to PC, in AC/PC plane

·         GPi (globus pallidum interna): 19-21 lateral from midline, 2mm anterior to MC (3-4mm anterior to IC), 5mm below AC/PC plane (2mm above optic tract)

 

Parkinson’s Disease

·         Etiology unknown. Decreased neurons in SNpc (normally inhibits GPi, which itself inhibits thalamus), DMN vagus & locus ceruleus. Path: Lewy bodies (eosinophilic intracytoplasmic inclusions with halo).

·         Basal Ganglia Neuroanatomy

·         Symptoms: resting (pill-rolling) tremor, bradykinesia, cogwheel rigidity. Also: micrographia, decreased blink, masked facies, festinating gain, pain in 50%, GI problems, dysautonomia, weight loss. Symptoms usually asymmetric. 20% have dementia. Diagnosis is clinical – 2 cardinal signs and response to levodopa.

·         Parkinson’s Plus syndromes: DBS is ineffective, even when responsive to levodopa.

o    Parkinsonism: 80% due to Parkinsons disease, 10% Parkinsons-Plus (MSA, PSP, CBGD, diffuse lewy body dz), 10% secondary. (drugs: neuroleptics, reserpine, Ca-channel blockers, lithium)

o    Multisystem atrophy (MSA): Younger. Path: α-synuclein positive glial cytoplasmic inclusions, no Lewy bodies. Poor response to dopamine. Includes:

·         Striatonigral degeneration: syncope, stridor.  Putamen atrophy

·         Olivopontocerebellar atrophy: AD, Chr 6, 15yo, LE ataxia, atrophy middle cerebral peduncle

·         Shy-Drager: autonomic probs, impotence, no lewy bodies(?); loss in putamen, SN, & interomediolateral horn cells

o    Progressive Supranuclear Palsy (PSP): downgaze palsy, pseudobulbar, gait palsy, eyelid freezing, no tremor, symmetric. MR: atrophy of midbrain & tectum. 70yos. No treatment.

o    Corticalbasal Degeneration (CBD): Parkinsonism, cortical signs (apraxia, myoclonus) and alien limb. No treatment.

Treatment:

Medical:

·         Sinemet: Dopamine + carbidopa (a dopa decarboxylase inhibitor). SE: N/V, orthostatis, arrythmias, on-off periods, dyskinesias (Tx B6). Contraindicated with Monamine Oxidase Inhibitors (MAOIs).

·         benztropin (Cogentin)/ Artane: anticholinergics.

·         Amantadine: Releases dopamine. Loses effect with time.

·         Bromocriptine/ pergolide: Stimulates D2 receptors. SE: vasoconstriction, fibrosis (bromocriptine is used for prolactinoma, pergolide isn’t).

·         Selegiline/ Eldypryl: MAOI. Slows progression. deprenyl: MAOBI.

Surgery

Modalities

·         Lesioning: GPi, STN (VIM thalamus)

·         Deep Brain Stimulation (DBS): of STN, (also GPi, Vim thalamus.). Up  to 35% of patients develop tolerance (for tremor)

o    DBS may be used in patients with cardiac pacemakers

·         Radiosurgery: only Vim Thalamus. 130Gy margin dose.  One 4mm collimator. Success: 82% good response. Onset 2mos.  SE: Dysarthria.

·         Experimental surgeries: Fetal mesencephalic transplantation into SN caused dyskinesias, some improvement <60yo. Adrenal medullary transplant abandoned.

·         Historical: Ligation of anterior choroidal artery

Locations

1. Pallidotomy: posteromedial GPi (6mm lesion) Usually done unilaterally only due to cognitive risk.

Indications: refractory to meds, dopa-induced dyskinesia (90% success), rigidity (75%), bradykinesia (85%), on-off, dystonia (tremor only 57% success). 

SE: field cut 3%, dysarthria 8%, hemiparesis, cognitive probs if bilateral.

CI: dementia (­ cognitive probs), ipsilateral hemianopsia, >85yo, 2° parkinsonism.

Withold meds day of surgery. Avoid IC (medial), optic tract (inferior). Can last >5yrs.

2. STN stimulation: May be done bilaterally. FDA approved 2003.

Effective for bradykinesia, tremor, rigidity. Medication reduced or eliminated (rarely with pallidotomy – overall results better, however more expensive $36K vs $12K).

Improved gait usually requires bilateral stimulation.

Appears to be 10% more effective than GPi stimulation.

STN can be seen on T2 low bandwidth. Position variable enough that microelectrode recording is needed. (JN3/04)

Usually done with microelectrode recording

SE: cognitive decline, depression, hypophonia. Effect declines with time. Mechanism unknown. Also effective in essential tremor.

Stimulation SE: Hypothalamus (anterior): flushing, perspiration. Coticobulbar tract (lateral): dysarthria. Medial lemniscus (posterior): paresthesias. CNIII (inferior/anterior): diplopia. Internal capsule/ Corticospinal tract (laterally): tonic contraction. Optic tract (inferior with GPi): visual changes. Blepharospam indicates effective STN stimulation.

·         Reviews: Starr PA N11/03 (Operative Nuances)

·         Videos: Starr PA N11/03

3. Thalamotomy or VIM DBS: VL: tremor/rigidity. VIM/VOP: tremor.

Complications: confusion, speech abnormality (­ w/ bilateral).

Done under local with MRI guidance

Thalamotomy – RF lesion at 75°. Bilateral not recommended.

VIM DBS – can be done bilaterally

 

Essential Tremor

·         Occurs in elderly. Familial: Autosomal dominant with variable penetrance, 60% of cases. Sporadic in 40%.

·         Bilateral action (not rest) tremor of hand/arms or head. No other neurologic signs. Relieved with alcohol.

·         Treatment: Propanolol, primadone.

·         VIM thalamotomy or STN stimulation. (Neurologist 9/04)

 

Dystonia

·         Sustained muscle contractions causing twisting, repetitive movements. Can be local or generalized, primary (idiopathic) or secondary to brain insult.

·         Primary: 30% have autosomal dominant DYT1 mutation

·         Treatment:

o    Medical, IT baclofen: often ineffective.

o    Pallidotomy or GPi DBS equally effective in primary and cervical dystonia.

·         Neither effective in secondary dystonia or patients with any MRI basal ganglia abnormality (although single center trial showed benefit DBS Pretto TE JN9/08 - VIDEO).

 

Torticollis

·         Treatment: CN11 neurectomy & upper cervical ventral rhizotomies (97% success), thalamotomy (66% success), MVD of CN11 (70% success), DCS, Botox

o    Selective peripheral denervation (Bertrand procedure): denervation and/or myotomy of sternocleidomastoid and/or levator scapulae and unilateral or bilateral ramisectomy

 

Hemifacial spasm

·         Intermittent, painless. Begins ocular, goes caudally. Persists during sleep. Females. Facial weakness may occur with advanced HFS.

o    Dx: MRI (no angio).  

o    DDx: Blepharospasm (bilateral), focal seizures (can check EEG).

o    Atypical spasm begins in buccal muscles, usually dorsal-rostral surface, harder to treat or preserve hearing.

·         Treatment:

o    Botox – injections q3-4mos for life (Tegretol, Baclofen).

o    MVD:

·         34% AICA, 31% PICA, 31% both, 4% basilar. Vessel usually contacts ventrocaudal surface of CN VII. May be on pontine surface or pontomedullary sulcus (Campos-Benitez M JN9/08)

·         Dissect DREZ only, not distal.

·         Intraop BAERS (Peak V latency delay: 0.6ms = warning, 1.0ms = critical). (Not used by all – see Dannenbaum M JN9/08)

·         SE: deafness (3-10%) > facial weakness (1%). Check contralateral hearing preop (audiogram).

·         Success 94%, 10% recurrence, 86% at 1mo.

·         Some use papaverine intraop.

·         HFS may persist for up to 3 months postop.

 

Idiopathic Intracranial Hypertension (IIH, Pseudotumor Cerebri):

·         Dandy criteria: symptomatic, no localizing findings (except CN6, 7 palsy), alert, normal CT/MRI, ICP >25.

·         Obese women most common, 20-45yo. Usually self-limited.

o    Usually transient during pregnancy – do not give Diamox 1st trimester.

·         Sxs: Headaches in nearly all – worse in am, with Valsalva. Also transient visual changes.

o    Papilledema in almost all (rarely absent – not necessary for diagnosis).

·         Ventricles may be normal or slit. Empty sella and enlarged optic n. sheath in 50%.

·         LP: Some asymptomatic obese women may have ICP > 25. CSF normal.

·         Associated with vitamin A & retinoids, antibiotics (tetracycline), hormones, steroid withdrawal, lithium. Stop meds if possible (stopping OCPs not necessary). Also associated with lupus, uremia, etc.

·         Blindness most significant sequelae – occurs in 25%. Can be rapid. Follow visual fields.

·         Treatment: Weight loss. Diamox (SR 500mg BID, teratogenic) ± Decadron (for acute blindness). Surgery for progressive visual loss or severe symptoms despite medical treatment:

1. Serial LPs: cumbersome

2. Subtemporal decompression: historical

3. Optic nerve fenestration: 90% successful. Unilateral fenestration appears to lower ICP, improves vision bilaterally and CN deficits, help HAs (debated). 2% risk of blindness.

4. LP shunt: Use horizontal (high pressure) – vertical (medium) valve. Complications: failure 55% in 1 year, overdrainage 15%, lumbar radiculopathy 5%, infection 1%, acquired Chiari and syringomyelia.

5. VP shunt: for repeated LP failure. Consider using stereotactic guidance for catheter placement with slit ventricles.

o    Debated whether ONSF or LP shunt is best. Have equivalent efficacy.

 

Empty Sella syndrome

·         1° (incompetent diaphragm) or 2° (surgery, stroke, etc). 

·         Sxs: HA, CSF rhinorrhea, visual loss, amenorrhea-galactorrhea.

·         Surgery only for CSF rhinorrhea – transsphenoidal repair ± lumbar drain. Shunt may cause pneumocephalus

·         Sheehans syndrome: ischemic necrosis 2° to intrapartum shock

 

Intracranial hypotension

·         Causes dural enhancement on MRI/CT.

o    Differential diagnosis of diffuse dural enhancement

·         Causes include shunts, CSF leaks. Spontaneous (SIH) usually result of rupture of spinal nerve root cyst into epidural space.

·         May occur with abducent palsy, tinnitus, and other symptoms.

·         Most resolve spontaneously.  May be treated with blood patches

 

“Brain Sag”: cause of postoperative deterioration with lumbar CSF drainage.  Reversed by the Trendelenberg position

 

Spontaneous cranial CSF leak

·         Due to sinonasal encephalocoeles (congenital or acquired), agenesis of the anterior fossa, empty sella, sinus infection, tumor.

·         See traumatic CSF leak for management.

 

Spontaneous spinal CSF leaks

·         May be due to osteophytes, dural tears, absent nerve root sheaths.  Connective tissue disorders may predispose.

·         Causes postural headaches.

·         MRI: dural enhancement, downward displacement of cerebrum. Diagnosis: Myelogram. (Low opening pressure on LP).

·         Treatment: Most resolve spontaneously. Bedrest, blood patch, surgical repair. (JN11/03)

 

Pneumocephalus

·         Air in the intracranial compartment

·         Due to communication with air sinuses or atmosphere

·         Due to bony and dural disruption

·         May be: traumatic (e.g. skull fracture), post-surgical (e.g. transsphenoidal), or spontaneous (due to CSF leak – sinus infection, tumor etc)

·         If asymptomatic – no treatment necessary, will resolve

·         Tension pneumocephalus: symptomatic mass effect due to pneumocephalus

o    Can evacuate with a spinal needle thru burr hole. Avoid N2O.

 

Normal Pressure Hydrocephalus (NPH)

·         Term coined by Hakim 1964. Idiopathic cases may be caused by unrecognized SAH, meningitis, etc.

·         “Guidelines”: Marmarou et al. Neurosurgery 9/05 Supplement. (Not universally accepted).

·         Symptoms: triad of dementia, gait instability, and incontinence. Usually occurs in the elderly.

·         Diagnosis:

o    Primarily clinical based on symptoms, however triad has PPV only 65% and NPV 82%.  No test sufficiently predictive (see JN 12/06). No RCTs exist.

o    Role of confirmatory tests versus shunt placement based on symptoms alone controversial: see JN12/06.

·         Some authors have suggested that the only reliable means of validating a diagnosis of INPH is to document a positive response to shunt placement (Ojemann RG JN69)

o    DDX:

·         Parkinsons – tremor, shuffling gait, late dementia, late incontinence. Improves with levodopa.

·         Dementias: Alzheimer’s, Multi-infarct (step-wise decline), Depression (Pseudo-dementia), Picks – all generally lack gait disturbance and late incontinence.

·         May also mimic chronic unrecognized communicating hydrocephlus (SAH, trauma)

·         In RCT shunting for Alzheimers showed no benefit (Silverberg Neurology 2008)

o    CT/MRI: Communicating hydrocephalus.

·         Marmarou: “it is clear that the prognostic value of CT/MRI scans is limited”

o    High-volume LP: remove 40-50cc (Marmarou) and look for clinical improvement. OP usually normal. Consider ambulatory lumbar drain trial. If positive then highly predicative, negative response is unreliable.

·         Marmarou: “A positive response to a 40- to 50-ml tap test has a higher degree of certainty for a favorable response to shunt placement than can be obtained by clinical examination. However, the tap test cannot be used as an exclusionary test because of its low sensitivity (26–61%). Determination of the CSF outflow resistance via an infusion test carries a higher sensitivity (57–100%) compared with the tap test and a similar positive predictive value of 75 to 92%. Prolonged external lumbar drainage in excess of 300 ml is associated with high sensitivity (50–100%) and high positive predictive value” (80–100%).

o    Radionuclide Cisternography:

·         Reflux into the ventricular system (and Sylvian fissures) with no ascent to the cerebral convexities within 24hrs. Ventricular activity persisting >48hrs implies good response to shunting.

·         Positive and negative predictive value only 50% - not recommended by some but commonly used.

·         Treatment:

o    CSF Shunt: 66% improve.

·         VP, LP shunts used.

·         Fixed and adjustable pressure valves used as a matter of preference.

o    Incontinence improves first.

o    Endoscopic third ventriculostomy has been used (N7/04)

o    Better outcome seen with minimal change in ventricular size than in patients with a marked decrease

 

Spasticity:

·         Upper motor neuron lesion – cortex to spinal cord. Increased muscle tone, resistance to movement, hyperreflexia.

·         Graded by Ashworth score

·         Treatment:

o    Medical: Valium, Baclofen, Dantrolene

o    Botox – local only; lasts 3mo.

o    Introthecal Baclofen pump: Use for potentially ambulatory patients. Test doses given to assess response (50µg then 100µg).

·         IT Baclofen Overdose: stop pump, IV physostigmine, move to ICU for possible intubation, remove 30ml from side-port or by LP (some say last is ineffective)

·         IT Baclofen Withdrawal: fever, tachycardia, HTN, spasticity. Give baclofen – oral or via LP – and fix pump/catheter.

o    Selective dorsal rhizotomies: intraoperative EMG to preserve “useful” spasticity.  Preserves ambulation.

o    Also: percutaneous radiofrequency foraminal rhizotomies, neurectomies, myelotomies (midline “T”)

 

Intrathecal Pumps

·         Used for spasticity (baclofen), pain (morphine)

·         Can check CSF via side port

·         Catheter-Tip Granulomas may form – require discontinuation of therapy or removal

·         Programmable Pumps: Medtronic Synchromed II

 

Facial Palsy: can anastamose CN12, 11, or 9 to CN7 (Campero A N9/07)

 

Psychosurgery

OCD (Obsessive-Compulsive disorder)

Treatment:

·         Bilateral anterior cingulotomy. Only 6-30% permanently respond (MGH reports 50% success). Many relapse within 1yr – may need repeat procedure. Also used for major depression. Target: 2.5cm posterior to tip of frontal horn.

·         Bilateral anterior capsulotomy (anterior limb of internal capsule)

·         Limbic leucotomy.

·         Above may be done stereotactically or with SRS.

 

Depression

·         Vagal nerve stimulation was approved for treatment of major depression in 2005

 

 

 

 


Pain

 

 

Cancer Pain

·         IT pump for life expectancy over 3-6 mos, otherwise destructive procedures

 

 

Neurostimulation for Pain

·         Neurostimulation for pain review: Coffey RJ JN8/06. NF12/06.

 

Deep Brain Stimulation for Pain

·         Periacqueductal grey (PAG).  SE: diplopia, anxiety.

·         Periventricular grey (PVG): Safest.

·         VPL/VPM

·         Not FDA approved

 

Motor Cortex Stimulation for Pain

·         MCS is unlabeled for any indication in the US. No RCTs.

·         For constant neuropathic pain – anesthesia dolorosa, thalamic stroke

·         Occipital nerve stimulation for headache: No RCTs

·         Reviews: Fontaine D JN2/09

·         Videos: CNS University of Neurosurgery

 

Spinal Cord Stimulator (Dorsal column stimulator)

·         Placed epidurally. Works when placed ventrally also (for unknown reasons).

·         Lead tips C3-C6 for UE, T10-T11 for LE.

·         Done awake w/propofol & local anesthesia. May be done percutaneously of via laminectomy, with RF-controlled receiver or IPG.

·         Permanent implantation preceded  by trial

·         Psychological screening used preoperatively

·         Results: Few RCTs.

o    Metaanalysis (n=3679), success rates: SCI, failed-back, phantom limb = 60%, peripheral neuropathy = 70%, ischemic limb pain (PVD), angina pectoris, postherpetic neuralgia, CPRS = 80%.

o    Poor for root avulsion, or cancer.

o    In RSD response may be predicted by sympathetic blockade.

o    Used commonly for angina in Europe (off-label in US)

o    25 to 50% of patients in whom a preimplantation trial is successful report loss of analgesia within 12 to 24 months (Doleys DM NF 12/06)

·         MRI with DCS has been reported (Sha RV 04)

·         SCS hardware infection: remove everything.

·         SCS manufacturers: Medtronic, ANS, Boston Scientific

·         Videos: CNS University of Neurosurgery

 

 

Destructive Procedures for Pain

·         Review: Cetas JS JN9/08

 

Cingulotomy: must be bilateral; recurs 3mo; SE: 10-30% flat affect

 

Medial Thalamotomy: head/neck pain. SE:  20-70% cognitive probs, aphasia. Controversial – rarely used.

 

Mesencephalotomy: head/neck pain. Stereotactic. Diplopia. Preferred.

 

Hypophysectomy

·         For severe bone pain in breast or prostate cancer

·         Done with radiosurgery, open resection, or alcohol ablation

 

Cordotomy

·         Unilateral pain below nipple, terminal patients, aching, deafferentiation pain

·         Open: C1/2 or thoracic laminotomies; Cut contralateral spinothalamic tract, start anterior to dentate, 5mm deep; Check PFTs, diaphragm function preop

·         Percutaneous: For patients with pain at or below C5 with limited life expectancy. Done awake, use stimulation. Done at C1/2 (contralateral side). Use fluoroscopy.

·         Success: 94% initial; 60% 1yr; 40% 2yr. SE: paresis, incontinence, Ondine’s curse

 

Commisural Myelotomy: bilateral pain, thoracic & below. Laminectomy 3 levels above – Penfield #4 (or similar) inserted in midline sulcus to central canal, sectioned from T10 to 2 levels above conus (avoid bladder dysfunction); 60% success

 

Punctate midline myelotomy: for pelvic and visceral pain

 

DREZ lesion (myelotomy/rhizotomy): good (50-70%) for nerve root/ brachial plexus avulsion for patients with no return of function. Not generally for cancer pain.

·         Prone. Laminectomy. Find roots above/below to locate DREZ. RF or bipolar lesioning, 4-5mm deep (substantia gelatinosa/Lissauers tract)

·          Reviews: Kanpolat Y ON3/08 (Operative Nuances)

·         Videos: Kanoplat Y ON3/08

 

Intrathecal pumps: For nociceptive cancer pain above C5. Suggest IT trial 1st

·         IT morphine overdose: stop pump, move to ICU for possible intubation, IV naloxone, remove CSF via side port

 

Complex Regional Pain Syndrome (CRPS)

·         Type I = Reflex Sympathetic Dystrophy (RSD), no nerve injury.

·         Type II = Causalgia, due to incomplete major nerve injury (ie GSW).

·         Both types can be sympathetically maintained pain (SMP) or sympathetically independent pain (SIP).

·         Etiology unknown (epiphatic transmission discredited). Most have onset <24hrs, usually within 1mo.

·         Sxs: Hyperesthesia (not hypesthesia) Triad: burning pain, autonomic dysfunction (­ or ¯ sweating & hair, vasoconstriction or dilation), trophic changes. Sudeks atrophy (skin, bone, etc – not nerve).

·         Dx: Sympathetic block: Stellate for UE, lumbar for LE. Confirmed by 1ºC increased temperature. Questionable – failed RCT.

·         Treatment:

o    TCA (Elavil), Neurontin, Tegretol, reserpine

o    Guanethidine sympathetic block (18-25% success, repeatable)

o    Spinal Cord Stimulator

o    Intrathecal opiates (often with clonidine or bupivicaine)

o    Sympathectomy (T2-3): evidence is scant. (Warm, reddish extremity and Horners for UE confirm successful sympathectomy)

o    Nerve surgery, other ablative treatment (DREZ lesioning, cordotomy) ineffective

Deafferentiation Pain

·         DREZ coagulation may be effective

·         Reinnervation Pain treated medically only; usually resolves

 

Sympathectomy

·         Used for hyperhidrosis, Raynauds, angina, RSD/CRPS, peripheral vascular disease.

·         Resect 2nd ± 3rd thoracic ganglia for palmar. Add 4th for axillary hyperhidrosis. (leave T1 to prevent Horners), 2nd & 3rd (±L1) for LE

·         Approaches: supraclavicular, transaxillary, midline posterior costotransversectomy, thoracoscopic, percutaneous radiofrequency.

·         Success: hyperhidrosis >90%.

·         Complications: Thoracic: bradycardia (usually asymptomatic). Recurrent hyperhydrosis common (JN:S2/05). Lumbar: retrograde ejaculation.

·         Lumbar sympathectomy for RSD: 2nd & 3rd lumbar sympathetic ganglion resected via retroperitoneal approach

 

Otalgia

·         May come from CN 5,7,9, or 10. Give trial of TGN meds. Intractable: explore CNs – MVD vs sectioning (nervus intermedius, 9, upper 2 roots of 10)

 

Trigeminal neuralgia

·         Criteria: Sharp, lacinating, intermittent pain. Unilateral. No neurologic deficits. Sensory trigger common.

·         Due to epiphatic transmission.

·         More common on right. V2&V3> V2> V3> V1&2> V1. Bilateral or V1 think MS.

·         Onset >50yo.

·         Trigeminal Anatomy

·         Diagnosis: MRI if atypical (young, bilateral, V1) or considering surgery.  Response to tegretol predictive.

o    DDx: herpes zoster (shingles) or post-herpetic neuralgia if resolved (continuous pain), dental pain, TMJ pain, temporal arteritis.

§  Look for vesicles on TM (Ramay-Hunt)

·         Secondary TN: due to multiple sclerosis, tumors, etc. Much less responsive to treatment

·         Atypical facial pain: constant, dull, without trigger or otherwise atypical for trigeminal neuralgia.

Treatment

·         Medical: Tegretol > dilantin > baclofen, neurontin, elavil, Lyrica.

o    Tegretol: 200mg TID, to 1600mg/day. May cause leucopenia, hepatitis. No levels – titrate to side effects.

·         Surgical (see JN2/05):

o    Success (2-year): MVD 90%, balloon compression 80%, RFR and glycerol 65%, SRS 60%. 3 year: balloon 70%, RFR 62%, Glycerol 55%.

o    Complications (trigeminal neuropathy): RFR = 30%, glycerol = 25%, BC = 15%, SRS = 10% 

·         Microvascular Decompression (MVD):

o    In 80% compression is by SCA (also AICA, persistent primitive trigeminal artery). In 5% of cases compression is primarily venous (transverse pontine & trigeminal veins) (N8/04)

o    Indications: >5yr survival, <65yo, failed PTR, V1 (less risk of keratitis than PTR).

o    85-95% initial success, 70% at 10yrs.

§  MVD more successful for lacinating (vs. constant) pain (Miller JP JN4/09)

o    Preoperative imaging: Miller J JN3/08. 3T MRI used.

o    Complications: hearing loss (check contralateral hearing preop, audiogram)

§  Mortality 0.3%, neurologic morbidity 2% (higher in redos, vertebrobasilar dolichoectasia).

§  Less risk of facial numbness than PTR. No anesthesia dolorosa. Small pontine infarctions occur on MRI in 24%.

·         Percutaneous Trigeminal Rhizotomy (PTR):

o    Lesioning methods: Radiofrequency (RFR), ballon compression (BC), glycerol injection.

o    Bradycardia, HTN may occur (consider atropine preop).

o    Look for ICA on preop imaging

o    Straight or curved electode (5mm 1div, 7.5mm 2 div, 10mm 3div).  Place needle 3cm lateral to oral commissure. Aim 3cm anterior to EAM, medial pupillary line. Palpate intraorally. Patient winces when entering foramen ovale. Obtain CSF (in trigeminal cistern). Stimulate to reproduce pain before lesioning.

o    SE: Numbness in 100%. Paresthesias/ dysesthesias 20%, anaesthesia dolorosa 4%, masseter weakness, ¯ hearing (tensor tympani), EOM paresis, neuroparalytic keratitis (2%).

§  Aneathesia dolorosa treatment: Meds (TCAs), trigeminal tractotomy/nucleotomy, open (Sjoquist) or percutaneous trigeminal DREZ lesion, motor cortex stimulation

o    See N4/04. Glycerol: JN2/05

·         Radiosurgery:

o    Success: 70% have >50% improvement at 3yrs, 55% no pain with meds, 35% pain-free.

§  58% response for secondary TN, 0% for atypical. Several reports show good response in TN 2° to multiple sclerosis

§  13% relapse (at avg 15mos). 

§  Not as good as initial MVD, but as good for second procedure.

§  Subsequent MVD is no more difficult after SRS (JN1/05S).

§  Right-side statistically significant higher success rate (JN3/05).

o    SE: 10% facial numbness, 12% other complications.

§  New facial numbness correlates with treatment response (JN3/05)

o    Takes days to 3 months to work. All improvement occurs by 1 year, most by 6 mos.

o    80 (70-90) Gy. One 4-5mm isocenter. Two isocenters and doses >85Gy also used (JN12/06S). Brainstem surface at 30% isodose line, center at DREZ

§  For repeat SRS: 50-60Gy, anterior to 1st target. (see JN12/06S)

o    See JN3/05.

·         Also: peripheral neurectomy (supraorbital, infrorbital, inf. dental nerves only; nonoperative candidates); Intradural neurectomy (failed PTR w/ preexisting CN5 anaesthesia. V1 superior, V3 inferior. Cut lower ½)

·         Raeders syndrome: V1 & V2 pain with oculosympathetic paralysis – ptosis and miosis (no anhydrosis-pseudoHorners); due to ICA disease

·         Tic convulsive: TGN w/hemifacial spasm

 

Glossopharyngeal neuralgia

·         Pain in ear, tongue, tonsil, and angle of jaw. 10% have vagal bradycardia/ asystole.

·         Dx: cocanization of tonsillar fossa relieves the pain.

·         DDx: primary ear/throat disorder, Ramsay-Hunt (check TM for vesicles)

·         Eagle’s syndrome: enlongated styloid process causes compression of CN9

·         Treatment:

1.     MVD (PICA)

2.     Rhizotomy (9 & top 2 roots of 10). 11% risk of hoarseness/dysphagia (also facial paresis). Significant dysphagia is rare.  Cardiac instability may occur intraop, give atropine before manipulating nerve. Monitoring CN9-10 not helpful. (N4/04)

 

Geniculate neuralgia: otalgia, prosopalgia (deep facial structures). Treatment: symptomatic

 

Postherpetic neuralgia: Persists >1-3mos after zoster. Lidocaine patch, TCAs (Elavil), Neurontin, IT lidocaine, Zostrix. Surgery controversial.

·         Thoracic ganglionectomy: Extended foraminotomy. Cut/clip ganglion in foramen. 3 levels – 1 above and below. Diagnose levels with lidocaine blocks.

 

Neurogenic hypertension: Basilar artery on left rostral ventrolateral medulla (RVLM), responds to MVD; may also be due to basilar impression & responsive to odontoidectomy.

 

Intercostal neuralgia: Tx: intercostals nerve blocks

 

Occipital neuralgia: Occipital nerve stimulation, Block, TENS.

·         Upper cervical ganglionectomy (C2 & C3), neurolysis/decompression, neurectomy (recurs)

 

Neuropathic pain:  Neurontin, TCAs, other AEDS, lidocaine gel/ patch, capsacin

 

Cluster Headache: Radiosurgery of the trigeminal nerve has been used for chronic refractory cases, but its efficacy is unclear (N12/06)

 

Microvascular Decompression (MVD)

·         Used for trigeminal neuralgia, hemifacial spasm, glossopharyngeal neuralgia.  Also reported for torticollis

  • Refractory essential hypertension: decompression of the left rostral anteromedial medulla. Janetta reported 75% success.

·         Check contralateral hearing preop (may cause ipsilateral hearing loss)

·         Intraop BAERS (Peak V latency delay: 0.6ms = warning, 1.0ms = critical).

·         Retrosigmoid craniotomy

·         Janetta stresses avoiding cerebellar retraction, use CSF drainage. 2mm retractor used, arachnoid dissected on cerebellar side only to protect CN. Dissect vessels off DREZ only (not distal? Others say whole nerve must be dissected (vs HFS) – N12/03). Place insulating sponge on vessel.

·         Superior petrosal veins may be cut and divided when multiple veins exist and it is not the single main drainer. Dandy’s vein (petrosal vein) must be watched for.

·         Pexy stitch on petrosal surface may be used to keep vessel off nerve with 8-0 nylon, or Teflon and fibrin glue.

 

Facial Nerve Reanimation

·         Primary anastamosis or cable graft if transected – 10-0 Nurolon

·         Facial-hypoglossal anastamosis: some wait 6-9mos Postop following EMG

o    May use partial anastamosis (hemihypoglossal) to avoid tongue atrophy

o    Intratemporal: Donzelli R N12/03

 

 

Revised 6/1/09

Text Copyright 2009


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